The word lad means "a boy, a young man." How old was Isaac at this time? The Hebrew word translated "young men," although plural, is the same as the word for "lad." The Jewish historian Josephus gives his age as 25, while rabbinic tradition says he was 36. Other commentators suggest he was 33. Because Isaac's life parallels the life of Christ to such an extent, that he was 33 years old at this time feels right.
Abraham tells his servants, "We will come back to you." Was he lying to them so as not to let Isaac know what was happening? It seems unlikely. Abraham is known as the "father of the faithful," and he had had the time to think the whole situation over. He knew that for God to deliver on His promises, Isaac would have to live. Hebrews 11:19 says Abraham acted as he did, "accounting that God was able to raise him [Isaac] up, even from the dead." He knew with ironclad certainty that God would resurrect his son. This in no way diminishes what Abraham had to do, for he still had to kill his own son! How many of us have that kind of faith?
Abraham's One God