What does Genesis 22:13 mean?
Earlier in Genesis 22, Isaac had asked his father where the lamb was that they were to sacrifice. Abraham replied that the God would provide for Himself the lamb (Genesis 22:8). Whether Abraham understood that God had provided for Himself Isaac or that another lamb would be provided, we don't know. In either case, God does exactly as Abraham said He would.The lamb, a ram, was presented ready-made to Abraham for the sacrifice. It was caught in a thicket right behind him. Abraham had only to replace Isaac with the ram and continue the offering. The ram given by God served as the substitute for Isaac in Abraham's burnt offering.
Again, we're told nothing of the emotions or words of Abraham or Isaac in response to all of this. What matters most to the Lord is made quite clear: their actions (James 2:20–22). Whatever he was feeling or thinking, Abraham trusted God and obeyed. He had passed the test, and the Lord had provided another offering as a way of worshipping God.
The call from heaven not to kill Isaac (Genesis 22:12), and the provision of a substitute sacrifice, serve to prove that Abraham's trust in God was well-placed. Just as He had in the past, God demonstrated that He was willing and able to keep His promises, and display His righteousness, even when limited human beings could not understand what was happening.