Then Mal'ak YHWH called to Abraham a second time from heaven

[beameup]

Then the Angel of the LORD called to Abraham a second time from heaven, and said, “By Myself I have sworn, declares YHWH, because you have done this thing and have not withheld your son, your only son, indeed I will greatly bless you, and I will greatly multiply your seed as the stars of the heavens and as the sand which is on the seashore; and your seed shall possess the gate of their enemies. In your seed all the nations of the earth shall be blessed, because you have obeyed My voice.”
Genesis 22:15-18

 

[beameup]

Now YHWH appeared to Abraham by the oaks of Mamre, while he was sitting at the tent door in the heat of the day. When he lifted up his eyes and looked, behold, THREE MEN were standing opposite him; and when he saw them, he ran from the tent door to meet them and bowed himself to the earth...
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Then the MEN rose up from there, and looked down toward Sodom; and Abraham was walking with them to send them off. YHWH said, “Shall I hide from Abraham what I am about to do, since Abraham will surely become a great and mighty nation, and in him all the nations of the earth will be blessed? - Genesis 18:1-2, 16-18

 

[beameup]

We can clearly see from Genesis 22 the "acting-out" of the sacrifice of an ONLY SON as an illustration of YHWH's plan to do the same. Clearly Abraham understood God's Plan for the future and was rewarded by God as a result of his FAITH.

BTW, Abraham had a prior son - Ishmael; however, God declared that Isaac was his only Son.