We first come across God’s covenant concerning circumcision in the Book of Genesis, a covenant is basically an agreement between two parties.
In the case of Genesis 17, it’s an agreement between God and Abraham which consisted of God promising Abraham and his descendants would inherit the Promised Land, that is Canaan, as long as Abraham and his descendants fully obeyed the Lord and remained faithful to Him all the days of their lives, Genesis 17:10-14.
In the above passage, we notice that there was a ‘sign’ for this covenant arrangement and the sign was circumcision. This would be the removal of the foreskin from every male child who was eight days old. The reason for this covenant was simply to learn not to trust in the flesh but to trust in God. The ceremony of circumcision was to be a sign of the covenant and so, everyone who was circumcised actually shared in this covenant.
It seems that even Abraham’s servants were to partake of the promises of the covenant because they too had to be circumcised which obviously meant they could be partakers of the covenant.
Notice that God knew things back then that scientists today have not long discovered. God commands that those who were eight days old were to be circumcised, why eight days? Because this was the earliest safe day to be circumcised because the blood was full of vitamin K, which helps with blood clotting, Genesis 17:23-27.
Straight away, that very same day we see Abraham, his family and his household obeying God and entering into that covenant relationship with God, Later we see that God reminds Moses that all males must be circumcised, Leviticus 12:3, and later still we read about how God commands Joshua to have all the male Israelites circumcised, Joshua 5:2-3. Circumcision was a ‘sign’ of their relationship with God and the basis for the law which required that all Jews be circumcised.
Let’s fast forward a few thousand years, after the church was established, but still, in its infancy, we find that some Jewish Christians who had left Judaism and become Christians were trying to mix Christianity with Judaism, they tried to add elements of the Jewish faith with the Christian faith. One of those elements from Judaism was circumcision, we read about this in Acts 15:1-35, and throughout the Book of Galatians.
Paul goes on to make his case that physical circumcision wasn’t required to be a Christian like it was in order to be a Jew.
Under the Holy Spirit’s guidance, Paul goes ahead and uses the mindset of the Jews concerning circumcision as a ‘sign’ that they had a covenant with God, Genesis 17:11, to teach them a very important lesson concerning baptism.
Throughout the book of Colossians Paul reminds the Christians that they don’t have to obey all the laws of Judaism in order for them to be Christians. He reminds them that they are in Christ, who is the Head of the church and its Christ who has all the rule and authority over everything, Colossians 2:10 and notice what he writes next.
After reminding them that they aren’t under the same covenant God made with Israel because that was nullified by Christ at the cross, Colossians 2:14, and we’re now under a new covenant relationship with God, Hebrews 8:6-13, which is Christ’s covenant.
Paul now says, just like physical circumcision was required as a ‘sign’ of the old covenant, God still requires ‘circumcision’ as a sign in the new covenant.
The difference is simply this, this isn’t a literal, fleshly, physical circumcision, this is a spiritual circumcision, ‘made without hands.’ And so, to emphasise what’s he’s speaking about, he says this spiritual circumcision happens when a person is baptised, that is fully immersed in water, Colossians 2:12 / Romans 6:3-4 / Galatians 3:26-27.
If anyone wanted to become a Jew, they needed to be physically circumcised, Joshua 5:6-7, in order to have that sign of the old covenant with God, to demonstrate that they belonged to God and had a relationship with Him.
Today, if anyone wants to become a Christian, then they too need to be spiritually circumcised, in order to have that sign of the new covenant with God, to demonstrate that they belong to God and have a relationship with Him, Matthew 28:18-20 / Mark 16:16.