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The Bible does not state the age of Isaac when he was offered as a sacrifice. But the scriptures give us some clues that show he was not a young boy but rather a young man at the time of the offering.
Abraham’s son was conceived when the father was 99 years old, Sarah was 90, and Ishmael was 13 (Genesis 17:1, 17, 25). When the boy was weaned (2-5 years) later, Hagar and Ishmael were dismissed from Abraham’s house and the covenant between Abraham and Abimelech took place (Genesis 21). And Genesis 21:34, says “And Abraham stayed in the land of the Philistines many days.” This verse suggests that many years (in biblical terms a day often refers to a year” lapsed to allow the boy to grow to be a young man.
In Genesis 22:1 it says that “after these things that God tested Abraham.” And after the sacrifice of Isaac came the news of Abraham’s relatives in Haran and then Sarah died at the age of 127 when Isaac was 37 (Genesis 23:1). So, there was a period of 35 years from weaning till the death of Sarah to allow for the chapter 21 and 22 to take place.
Also, the word “lad” that pointed to Abraham’s son in Genesis 22:5,12 doesn’t necessarily mean that Isaac was a young boy. For example, Joseph was called a lad at the age of seventeen (Genesis 37:2). In addition, Isaac must have been a young man to be able to carry the wood necessary for the large sacrifice (Genesis 22:6) because we are told that Abraham left his servants at the bottom of the mountain and went alone with his son to the place of offering. A small boy could not carry the bundle of wood. For these reasons Bible commentators have expressed their views about the age of Isaac as such:
Josephus wrote: “Now Isaac was twenty-five years old” (1.13.2).
Leupold wrote: “He may by this time have arrived at the age of some eighteen to twenty years” (1942, 1:625).
Adam Clarke wrote: “[I]t is more probable that he was now about thirty-three” (1:140, emp. in orig.).
Jamieson, Fausset, and Brown wrote that Isaac was “then upwards of twenty years of age” (n.d., p. 29).
Keil and Delitzsch wrote that “this son had grown into a young man” (1976, 1:248).
Morris said, “[T]he meaning in Isaac’s case should also be ‘young man’ ” (1976, p. 373).
Curtis Manor wrote that Isaac was “a youth of sufficient strength and agility to carry a load of firewood up a mountainside” (1994, p. 103).
Isaac submitted to the will of God and His father. In so doing, he was a type of the Messiah, the only begotten Son of God; whom God out of his great love to men gave to be an offering and a sacrifice for their sins (John 3:16).
In His service,