Question: "How old was Isaac when Abraham almost sacrificed him?"
Answer: To test Abraham’s faith, God once commanded him to sacrifice his promised son, Isaac. The Bible doesn’t specify how old Isaac was when he and his father made their trip to Moriah for the sacrifice. Because of Scripture’s silence on the matter, we must conclude that knowing Isaac’s age does not affect our understanding of the passage or our grasp of the lesson that God wants us to learn. But, to help satisfy curiosity, we can gather some clues of Isaac’s age from the text.
One clue is Genesis 22:7, where Isaac notices wood and fire but, seeing no animal, asks Abraham about it. This implies that Isaac is at least old enough to know what the proper sacrificial process is and perceptive enough to ask his father about it. This doesn’t tell us too much about his age, though, since it’s possible that even a young child might have noticed this.
Some limits are suggested by the chronology of Sarah’s life. Sarah gave birth to Isaac when she was 90 years old (Genesis 17:17). Sarah sent Ishmael away (sometime before the incident at Moriah) after Isaac was “weaned” (Genesis 21:8–10). Generally, weaning took place somewhere between the ages of 2 and 5. Sarah died (sometime after the incident at Moriah) at the age of 127. This means Isaac was older than 4 or 5 and younger than 36 or 37 when he was offered as a sacrifice. The phrases a long time in Genesis 21:34 and some time later in Genesis 22:1 suggest that a substantial amount of time elapsed between Isaac’s birth and the trip to Moriah. So, Isaac was certainly not an older man when he was to be offered as a sacrifice, but neither was he a toddler.
Another clue regarding how old Isaac was comes from Genesis 22:2, where Abraham is told to travel to Moriah, a three-or-four-day journey. The distance to be traveled certainly suggests that Isaac was old enough to care for himself and to help care for his over-100-year-old-father on such a trip.
The term boy or lad used to refer to Isaac (Genesis 21:5, 12) is translated from a flexible Hebrew term that does not necessarily refer to a young boy. Rather, the term encompasses a wide range of meanings—from a baby (e.g., Exodus 2:6; 2 Samuel 12:16) to a young man (e.g., Absalom in 2 Samuel 14:21; 18:5). It even can refer to a “steward” or “servant” (e.g., 2 Samuel 16:1) as well as a “junior officer” (1 Kings 20:14, 15, 17, 19). In Genesis 22:5 the servants that accompanied Abraham and Isaac are called “young men” (Genesis 22:3, 5, 19, ESV). The word translated “young men” is the same word applied to Isaac in verses 5 and 12.
Probably the most useful clue to how old Isaac was is Genesis 22:6. As they climb the mountain, Isaac is the one carrying the large pile of wood. Wood enough for a burnt sacrifice would have been fairly heavy. This fact tells us Isaac wasn’t a small child when he was to be sacrificed; he was at least a healthy teenager. Isaac’s age also adds an interesting dimension to the story. If he was strong enough to carry the wood up the mountain, then he was probably strong enough to resist being sacrificed and fend off Abraham if he had wanted to. The fact that Isaac allowed himself to be bound and placed on the altar (verse 9) shows that Isaac continued to trust his father.
Several commentators have weighed in on the question of how old Isaac was when he was to be sacrificed: 18 to 20 years old (Leupold, 1:625); 25 years old (Josephus, 1.13.2); about 33 years old (Adam Clarke, 1:140); and over 20 years old (Jamieson, Fausset, and Brown, p. 29).
Taking all the evidence, we can safely say that Isaac was a young man—not a young boy—when Abraham attempted to sacrifice him on Mt. Moriah.