In my opinion, the best way to answer the above question is by asking a more pertinent question, such as,

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"WHY WAS ABRAHAM THE ONLY PERSON GOD EVER ASKED TO SACRIFICE HIS SON?" 

 

Consider this.  In Judges 13:2-24, an angel appeared to Manoah’s barren wife and told her that she would have a son, Samson.  Later on both Manoah and his barren wife spoke again to the angel about their future son. 

 

Now think about the similarities between the story of the angel’s announcement to Manoah and his barren wife that they will have a son, and the better-known story of God’s announcement to Abraham and his barren wife Sarah that they too will have a son. 

 

Notice that God never asked Manoah to sacrifice Samson when Samson was a young child, yet God did ask Abraham to sacrifice Isaac when he was a young child.

 

Why was that?  Why did God never ask Manoah to sacrifice Samson, but instead asked Abraham to sacrifice Isaac? God’s reason couldn’t be to simply use Isaac as a “type of Christ”, because God could easily have told Manoah to sacrifice Samson as a young boy and then we would be talking about how Samson was a “type of Christ” instead of talking about how Isaac was a “type of Christ”. 

 

For that matter, God didn't ask Adam, Enoch, Noah, Isaac, Jacob, Joseph, Moses, Samuel, David, Solomon, Jehoshaphat, Hezekiah or Josiah to sacrifice THEIR firstborn sons either. 

 

So, 

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"WHY WAS ABRAHAM THE ONLY PERSON GOD EVER ASKED TO SACRIFICE HIS SON?" 

 

In other words, “What was so DIFFERENT about Abraham's relationship with God that prompted God to only ask Abraham (and no one else) to sacrifice his son?" 

 

Here is my opinion.  

 

Abraham was the ONLY person who ever lived who actually DOUBTED God’s promises a total of SIX different times despite being told 30 times directly or indirectly that Abraham would have a son. So God tested Abraham to prove to Abraham that there was NEVER any reason to doubt God’s promises from the very first time God told Abraham, “I will make you into a great nation” (a promise God gave to Abraham 25 years earlier, way back in Genesis 12:2). 

 

Here are the details of my reasoning. 

 

From the beginning of Genesis 12 through the end of Genesis 21, God told Abraham directly or indirectly at least THIRTY TIMES that Abraham would have a son. Specifically, God told Abraham he would have a SON (2x), have an HEIR (1x), have OFFSPRING (2x), have many DESCENDANTS (9x), GENERATIONS would come from him (3x), that he would be the FATHER of MANY NATIONS (3x), that KINGS would come from him (1x), that God would INCREASE HIS NUMBERS (1x) and that he would be VERY FRUITFUL (1x). God also told Abraham that Sarah would have a SON (5x), that Sarah would be the MOTHER OF NATIONS (1x), and that KINGS would come from her (1x). This totals at least THIRTY TIMES that God told Abraham directly or indirectly that he would have a son through whom Abraham would sire many generations. All these reassurances to Abraham were spread out over ten chapters (from Genesis 12 through 21) so most people don’t actually recognize just how many times God reassured Abraham over and over that Abraham would indeed have a son.

 

Yet Abraham clearly DOUBTED God’s promises SIX TIMES!  In fact, no one else in the entire Bible ever doubted God’s promises as much as Abraham did.  Despite having God appear to Abraham multiple times, despite Abraham speaking directly to God, and despite Abraham seeing God destroy Sodom and Gomorrah, and despite God telling Abraham directly or indirectly 30 times that Abraham will have a son, Abraham still doubted God’s promises a total of six times.  

 

For instance, immediately after God told Abram (TWICE) that he would inevitably have a son (in Genesis 12:2 and 12:7) Abraham already shows his FIRST DOUBT of God’s promise, by mistakenly believing that Pharaoh could THWART God’s promise by killing Abram and taking Sarai as his wife because Sarai was so beautiful.  So Abram told Sarai, “Say you are my sister, so that I will be treated well for your sake and my life will be spared because of you.”  (Genesis 12:13)  

 

But God protected Abram in Egypt and then, in Genesis 14:14-16, God protected Abram again, this time in a battle where Abram and roughly 321 men fought against 4 Kings and their 4 armies who captured Lot, thereby PROVING to Abram that NO ONE could ever THRWART God’s promise to Abram that Abram would have a child. 

 

Despite this, in Genesis 15:2 Abram expresses his SECOND DOUBT, “…what can you give me since I remain childless...You have given me no children…”

 

So, in response to Abram’s doubt, in Genesis 15:4-6, God tells Abram 3 additional times that he will have a SON, an HEIR and as many OFFSPRING as the stars.   Then, “Abram believed the Lord, and he credited it to him as righteousness.”

 

Abram’s belief sounds wonderful. Yet IMMEDIATELY AFTER Abram’s belief was “credited to him as righteousness”, Abram asked God for some ADDITIONAL SIGN of the TRUTH of God’s promise.  I interpret this as ABRAM’s THIRD DOUBT—a doubt that immediately followed his earlier “belief that was credited to him as righteousness”.  This is similar to the father of the possessed child in Mark 9:24, where the father says to Jesus, “Lord I believe.  Help my unbelief.”  And, just as the demon-possessed boy’s father’s faith is not as great as he would like it to be, likewise Abram’s faith in God’s promises is not as 100% COMPLETE as we have imagined it to be either.  So in Genesis 15:8, Abram asks God, “Sovereign Lord, how can I KNOW that I will gain possession of it?”  This is Abram’s THIRD DOUBT.  In Abram’s heart, he is seeking a sign, yet in Matthew 16:4, Jesus tells us that desiring a sign is NOT a demonstration of faith.  

 

Yet despite this, in Genesis 15:14-18, God gives Abram a sign anyway. Here God reassures Abram (yet again) that he will have DESCENDANTS (3x) and that there will be a FOURTH GENERATION of ABRAM’S DESCENDENTS (1x).  Then, God made a covenant with Abram and his DESCENDANTS (1x).  

 

Next, in Genesis 16:1, Sarai says to Abram,  “The Lord has kept me from having children. Go, sleep with my slave; perhaps I can build a family through her.”  This story not only reflects Sarai’s doubts, but because Abram agreed with Sarah’s plan, the story also reflects what I believe is Abram’s FOURTH DOUBT as well. 

 

In Genesis 17:1-16, Abram is now 99 years old, and so God tells Abram (now called Abraham) roughly 16 ADDITIONAL times that he will have a son.  God says to Abraham that God will INCREASE YOUR NUMBERS (1x), that NATIONS (1x) and KINGS (1x) will come from Abraham and that Abraham will be the FATHER OF MANY NATIONS (2x).  He tells Abraham that he will be VERY FRUITFUL (1x) and that Abraham will have DESCENDANTS (5x) and that GENERATIONS (2x) will be BORN IN HIS HOUSEHOLD (1x).  At that time, God also told Abraham that Sarah would have a SON, that Sarah would be the MOTHER OF NATIONS (1x), and that KINGS would come from her (1x).  

 

Yet immediately after this, in Genesis 17:17-18, Abraham has his FIFTH DOUBT.  For it is written:  “Abraham fell facedown; he laughed and said to himself, ‘Will a son be born to a man a hundred years old? Will Sarahbear a child at the age of ninety?’ And Abraham said to God, “If only Ishmael might live under your blessing!”  Here Abraham is imagining that God’s promises can only come true though Ishmael, a child conceived because Abraham mistakenly believed he had to ASSIST God in order for God to carry out his promises, therefore having a child through HAGAR instead of through Sarah.

 

Then God addresses Abraham’s FIFTH DOUBT by Abraham by telling Abraham again that Sarahwill have a SON (2x), mentions Isaac by NAME (2x), uses the pronoun “HIM” to refer to Isaac (2x) and says that all this will happen 12 months from then.  

 

In Genesis 18:10, God again says that Sarah will have a SON, then addresses Sarah’s doubt in 18:14 by asking, “IS ANYTHING TOO HARD FOR THE LORD? I will return to you at the appointed time next year, and SARAH WILL HAVE A SON (1x).”  Then God says, “Abraham will surely become a great and powerful NATION” (1x) and talks about Abraham directing his CHILDREN (1x).

 

Now because of their many sins, God could have destroyed Sodom AT ANY TIME within the past several years, yet IMMEDIATELY AFTER God asked Sarah, “Is ANYTHING too hard for the Lord?”, as if to prove to Abraham that NOTHING is too hard for the Lord (like giving a 100-year old man a son by a 90-year old woman), God immediately announces in the remainder of Genesis 18 that he intends to destroy Sodom and then DOES destroy Sodom in Genesis 19.  (The TIMING of God’s announcement can hardly be a coincidence.)

 

After seeing Sodom and Gomorrah supernaturally destroyed, at this point, it should be obvious to Abraham that NOTHING IS TOO HARD FOR THE LORD and that NOTHING CAN INTERFERE WITH GOD’S PLANS to give Abraham a son through Sarah. Now Abraham only needs the faith to trust God for just one more year (to have a son) and only needs to trust God for just THREE MORE MONTHS for Sarah to become pregnant.  But despite this, Abraham begins to doubt once again (Abraham’s SIXTH DOUBT), and so, when moving to live within the Philistine area, Abraham demonstrates ONE MORE TIME that he believes he must ASSIST God’s promises by taking steps to protect his own life.  To that end, Abraham starts a rumor in Genesis 20:2 that Sarah is only his sister and not his wife, so the Philistines won’t kill him to take his wife. So evidently, despite God having the power to destroy Sodom and Gomorrah, Abraham still believes that some things are TOO HARD FOR THE LORD and that God does NOT have the power to protect Abraham’s life while living within the land of the Philistines without Abraham starting a rumor that Sarah is NOT his wife.  In other words, Abraham STILL does not believe that God can honor his own promises to Abraham without Abraham’s personal ASSISTANCE.  That is the SIXTH TIME that Abraham has DOUBTED God’s promises!   

 

Finally, in Genesis 21:2, Sarah became pregnant and bore a son to Abraham in his old age, at the very time God had promised him. 

 

Then, in Genesis 21:22-23, it is written, “At that time Abimelek and Phicol the commander of his forces said to Abraham, “GOD IS WITH YOU IN EVERYTHING YOU DO. Now swear to me here before God that you will not deal falsely with me or my children or my descendants.”

 

Imagine that.  The nation that Abraham was afraid of is now afraid of Abraham and afraid of Abraham’s God, so they want to make a treaty with Abraham to protect themselves from Abraham (who has grown very rich and powerful by this time) and more importantly, from Abraham’s God.  But notice this.  It took the KING of the Philistines to teach Abraham that “Abraham’s GOD WAS WITH ABRAHAM IN EVERYTHINGABRAHAM DID”, and that Abraham’s God was as good as his word, so that Abraham NEVER needed to have doubted God’s 25-year-old promise that God would indeed be make Abraham “into a great NATION” 

 

Then, on the heels of Abimelek’s reassurance to Abraham that “NOTHING can THWART the promises of Abraham’s God”, the very next story is God’s test of Abraham to sacrifice Isaac.  

 

For it is written: “Then God said, ‘Take your son, your only son, whom you love—Isaac—and go to the region of Moriah. Sacrifice him there as a burnt offering on a mountain I will show you.’”  (Genesis 22:2)

 

So, without attempting to sound arrogant or dare to claim that I have anywhere near a perfect understanding of God’s mind, I believe that God responded to Abraham’s repetitive doubting of God’s promises by saying to himself, 

 

“Abraham, now that Isaac is finally born, are you 100% SURE (even NOW) that you believe my promises that you will have MANY GENERATIONS of descendants? I am going to test you to see if you are FINALLY 100% SURE that NOTHING at all can EVER thwart the promises of God.”

 

And THAT is why God ultimately tested Abraham (and ONLY Abraham) by asking Abraham if he would be willing to sacrifice Isaac and trust that God would simply raise him from the dead (Hebrews 11:9) in order for God to honor his 30 promises to Abraham that he would have a son Isaac that would be the father of many nations.

 

That being said, I believe God wanted to prove to us just how great Abraham’s faith actually was, because Abraham ONLY doubted God’s promise 6 times during those 25 years, whereas the rest of us would have doubted God far more than 6 times over those same 25 years.  However, given that Abraham did doubt 6 times, it makes sense that God would ultimately prove Abraham’s faith one more time by asking him to sacrifice his son Isaac to demonstrate to us that Abraham was now trusting that God would raise Isaac back from the dead just to keep his promise to Abraham.  I believe that God recognized the depth of Abraham’s faith 25 years earlier and therefore took those 25 years to set up the circumstances to prove to the world the depths of Abraham’s faith.  

 

So, why did God ask Abraham to sacrifice Isaac? Because 6 times Abraham doubted God’s promise that Abraham would have a son.  But why did God wait 25 years to honor his promise to Abraham, when God knew in advance that Abraham would doubt God 6 times and that this would compel God to ask Abraham to sacrifice Isaac?  To prove to us just how great this man’s faith actually was.