I don’t believe Abraham knew how it would turn out. He knew God had told him to sacrifice his son Isaac, and he also knew God had told him he would be the father of a multitude of nations, and that those nations would come through Isaac. And as the writer of Hebrews said, “Abraham considered that God was able to raise men from the dead; from which he also received Isaac back as a type.”
The Lord once told me that if I would trust Him to supply all my needs, I must be willing to give away even that which I needed. He then said I was to give away all the money we had to someone less fortunate. And although we had no income at the time, we gave it all away. We considered that the Lord was able to sustain us, whether we had anything, or not.
The result was that He supplied our needs in ways that we could have never imagined. I look back on it now, and it appears the Lord was testing me somewhat like He tested Abraham, though not as drastic.
So, no, Abraham didn’t know how it would turn out. When he told Isaac the Lord would provide for Himself the lamb for the burnt offering, I honestly think he thought Isaac would be the lamb, because he laid Isaac on the altar, bound him, and picked up the knife to slay him, Genesis 22:9, 10. He considered that God was able to raise the dead in order that His promise to Abraham could be fulfilled. In other words, Abraham considered the integrity of God to be such that His descendants would be through Isaac, one way or another. And he obeyed God.
Jon David Banks, God’s most unworthy servant