Jesus was circumcised because He was a child born of the seed of Abraham (Matthew 1:1-18). His parents were faithful Jews and brought Him to be circumcised on the 8th day, and then go through the purification requirements of Leviticus 12. Circumcision was a command of God to distinguish His people from the Gentile nations. A circumcised child communicates that he belongs to God and is a recipient of the covenant promises.
Abraham
We see circumcision first mentioned in Genesis 17:10-14 where Abraham is commanded to be circumcised and to circumcise his offspring.
“This is my covenant, which you shall keep, between me and you and your offspring after you: Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you. He who is eight days old among you shall be circumcised. Every male throughout your generations, whether born in your house or bought with your money from any foreigner who is not of your offspring, both he who is born in your house and he who is bought with your money, shall surely be circumcised. So shall my covenant be in your flesh an everlasting covenant. Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant.”
Jesus perfectly kept the law
In being circumcised, Jesus would walk in the covenant promise of Abraham. Through circumcision and His obedience, Jesus perfectly kept the law throughout His earthly ministry. Circumcision was His first step to following and fulfilling God’s law perfectly. Jesus affirms His obedience to God’s law where He says in Matthew 5:17-18 “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.” Jesus submitted to the laws of God and to the legitimate customs of the religious authorities of His day to demonstrate His perfection and sufficiency to redeem us from our sin.
No circumcision needed
Circumcision was a ceremonial law of the Old Testament that was abolished when Christ died and rose from the dead. No longer is circumcision a requirement for a person to be in a covenant relationship with God (see the first church council in Acts 15 as well as Galatians 2:1-16). Those who put their trust in Jesus Christ alone are part of God’s covenant community and are in right standing with God by faith. God does not look for our outward signs to demonstrate fidelity to Him. Instead, God looks for those who are circumcised in the heart (Deuteronomy 10:16; 30:6).