Genesis 22:8, 9
- ..., God will provide himself ‘a’ lamb for a burnt offering; ... (KJV)
- ..., God will provide for Himself ‘the’ lamb for a burnt offering, ... (The Interlinear Bible Hebrew-Greek-English & NKJV)
First, Hebrew does not have an indefinite article as per English "a". However, it does have the equivalent of a definite article as per English "the". In Hebrew, the definite article is an initial "h" attached to the word in question.
In Gen 22:8, the operative word is הַשֶּׂ֛ה (haś·śeh) which consists of the word for "lamb" שֶׂה prefixed by an "h". Thus, we should strictly translate "the lamb", or more correctly, "the sheep", or, "the goat", not necessarily "lamb".
This translation is not always that simple, but is correct in this case. The very fact that Abraham prophetically uttered such a sentence so pregnant with anticipatory meaning is just one of the factors that makes this story so profound - predicted THE lamb to come.
From the vantage point of the NT we now know that this enacted parable and prophecy saw its fulfillment in THE lamb of God (John 1:29, 1 Cor 5:7) who died as a propitiation (1 John 2:2, 4:10, Rom 3:25, Heb 2:17, etc) for us. That is, Jesus was treated as we deserve so that we can be treated as He deserves (2 Cor 5:21).
Thus, Isaac was not sacrified and did not die, but a ram was in his stead.