Thoughts distilled from J.V. Fesko’s Word, Water and Spirit, on the parallel between baptism and circumcision:
Circumcision was a symbolic cutting away. It was given in Genesis 17, to Abraham, as a sign of the covenant, a sign of faith according to Paul in Romans 5. In Deuteronomy 10:16, Moses tells the people to “circumcise the foreskin of your hearts, and be no more stiffnecked” showing us the real spiritual import of circumcision, the putting away of pride and stubbornness, and humbling oneself before God. It is significant that the sign of circumcision was given to Abraham not when he first was given the promise in Genesis 12, but in Genesis 17 after Abraham’s attempt to fulfill the promise of God through his own efforts, rather than trusting in God to fulfill it. It was Abraham’s pride that led to the giving of this most appropriate sign. But how does one circumcise their own hearts? They can’t, of course, and Moses promises in Deuteronomy 30:16 that the day would come when God would do that work. On the other hand, the one who rebels against the covenant and will not submit- he is “cut off” from his people.
Ultimately, though, it is Jesus who is “cut off” from His people, taking the sin of the people with Him, and emerges victorious.
Likewise, baptism is a symbolic washing- even a flood or deluge. Noah’s flood and the crossing of the Red Sea are both spoken of as symbolic baptisms, by Peter (1 Peter 2:20-22) and Paul (1 Corinthians 10:1-2) respectively. John the Baptist comes preaching a baptism of repentance (Luke 3:3) but warns the people that a judgment is coming, from which only repentance can save them (Luke 3:7-8). Some of those who are baptized, but do not repent, will be damned, swept away by the water like the world was in the flood, or like the Egyptians were in the Red Sea, or like many of the Israelites who fell in the wilderness outside the favor of God.
But once again, it is Jesus who is “baptized” into death, comes under the flood of God’s wrath, takes it on our behalf, and emerges victorious.
So baptism, like circumcision, represents an ordeal, a trial, that the people as a whole are put under. That trial is judged on the basis of faith, for both are symbols of faith, symbols specifically of a promise, and in each the promise is of Christ, the champion of the people who undergoes the full trial and is victorious. If we, by faith, come under the umbrella of His victory, repenting of sin and putting our trust in Him as the Anointed One, then we emerge triumphant. If not, the trial sweeps us away. We are cut off from the people; we are washed away in the flood.