Your only son

God tested Abraham.

God tested Abraham and said to him, “Abraham!” And he said, “Here I am.” He said, “Take your son, your only son Isaac, whom you love, and go to the land of Moriah, and offer him there as a burnt offering on one of the mountains of which I shall tell you.” So Abraham rose early in the morning, saddled his donkey, and took two of his young men with him, and his son Isaac. And he cut the wood for the burnt offering and arose and went to the place of which God had told him.
Genesis 22:1-3

Abraham obeyed but God stopped him from carrying out the sacrifice.

Then Abraham reached out his hand and took the knife to slaughter his son. But the angel of the LORD called to him from heaven and said, “Abraham, Abraham!”

And he said, “Here I am.”

He said, “Do not lay your hand on the boy or do anything to him, for now I know that you fear God, seeing you have not withheld your son, your only son, from me.”

And Abraham lifted up his eyes and looked, and behold, behind him was a ram, caught in a thicket by his horns. And Abraham went and took the ram and offered it up as a burnt offering instead of his son.
Genesis 22:10-13

There are some lessons we can learn from this.

Abraham’s willingness to give up for God what he prized most in the world sets an example that we should follow.

Abraham loved God so much that he was willing to sacrifice his only son for him.  God loved us so much that he was willing to sacrifice his only son to die for our sins.

The ram Abraham sacrificed instead of Isaac is an illustration of Jesus who was died in our place.

But skeptics raise two objections.

First they ask why God needed to test Abraham in the first place.  Isn’t God omniscient?  Didn’t he already know what Abraham would do in this situation?

They misunderstand the purpose of the test.  Of course God already knew what would happen.  He wasn’t testing Abraham the way a teacher tests students to find out how much they have learned.  The test was made because of the effect it would have on Abraham.

Count it all joy, my brothers, when you meet trials of various kinds, for you know that the testing of your faith produces steadfastness.
James 1:2-3

When God tests one of his followers it is always for that persons benefit, not because God needs to learn something about him.

The second objection is based on this phrase, “Take your son, your only son Isaac.”  Abraham had two sons, Isaac and Ishmael.  So why did God call Isaac Abraham’s only son?

When Abraham entered the land of Canaan God promised to make a great nation of his descendants.  Ten years had passed and Abraham’s wife hadn’t given birth to a child so Abraham fathered a son by her maid Hagar.  He named the boy Ishmael and thought that God would fulfill his promise through him but God had other plans.

And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her.”

Then Abraham fell on his face and laughed and said to himself, “Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?”

And Abraham said to God, “Oh that Ishmael might live before you!”

God said, “No, but Sarah your wife shall bear you a son, and you shall call his name Isaac. I will establish my covenant with him as an everlasting covenant for his offspring after him.”
Genesis 17:15-19

Isaac was Abraham’s only legitimate son, the one through whom God would fulfill the promises he had made.

By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises was in the act of offering up his only son, of whom it was said, “Through Isaac shall your offspring be named.”
Hebrews 11:17-18

Isaac was also Abraham’s only son because of an incident that had happened a few years earlier.

And the child grew and was weaned. And Abraham made a great feast on the day that Isaac was weaned.

But Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, laughing. So she said to Abraham, “Cast out this slave woman with her son, for the son of this slave woman shall not be heir with my son Isaac.”

And the thing was very displeasing to Abraham on account of his son. But God said to Abraham, “Be not displeased because of the boy and because of your slave woman. Whatever Sarah says to you, do as she tells you, for through Isaac shall your offspring be named.”
Genesis 21:8-12

Ishmael had been expelled from Abraham’s household and was no longer legally his son or heir.  Isaac was in fact Abraham’s only son.