What does Genesis 17:24 mean?

This verse repeats again that Abraham was 99 years old on the day God appeared to him and he was circumcised. Perhaps he was the oldest man ever to be circumcised, at least at that time. God's plan for future generations of Abraham's offspring was to use this ritual as a sign of the covenant with God, to be performed when they were eight days old (Genesis 17:12).

Circumcision is removing the foreskin from the penis. This symbolically represents many aspects of our relationship to God. It requires setting aside, or removing, a naturally-born part, just as our sinful desires need to be set aside in favor of following God. The area affected is more or less circular, which is a common symbol of eternity and constancy; this covenant was meant to be a permanent practice by Israel. It also represents the eternal and unchanging nature of God. Likewise, this ritual affects the organ of reproduction, signifying the passing of truth from generation to generation. In fact, circumcision creates a ring around the point through which passes the man's contribution to reproduction.

Circumcision is not required for believers in Christ, even though it is still part of God's unchanging covenant with the nation of Israel. In fact, in the New Testament era, the term "circumcision" will become shorthand for those who think their good deeds can earn them salvation (Galatians 5:1–6).