On the eighth day, Jesus was circumcised. It was the sign of the covenant between God and the offspring of Abraham, the father of many nations. God instructed Abraham that he and his descendants should keep God’s covenant, but we all failed. As David wrote:
The Lord looks down from heaven on the children of man,
to see if there are any who understand,
who seek after God.
They have all turned aside; together they have become corrupt;
there is none who does good,
not even one. Psalm 14:2-3
Therefore God came down to earth to keep the covenant for us – to accomplish our salvation Himself. The salvation David longed for came in the person of Jesus, who kept God’s Law perfectly that we might be saved. When it comes to keeping the Law, we are all equally hopeless; and we are all equally saved by Jesus – there is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus.
The Old Testament lesson is from the book of Genesis, chapter 17, verses 3b-14:
And God said to him, “Behold, my covenant is with you, and you shall be the father of a multitude of nations. No longer shall your name be called Abram, but your name shall be Abraham, for I have made you the father of a multitude of nations. I will make you exceedingly fruitful, and I will make you into nations, and kings shall come from you. And I will establish my covenant between me and you and your offspring after you throughout their generations for an everlasting covenant, to be God to you and to your offspring after you. And I will give to you and to your offspring after you the land of your sojournings, all the land of Canaan, for an everlasting possession, and I will be their God.”
And God said to Abraham, “As for you, you shall keep my covenant, you and your offspring after you throughout their generations. 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.”
The Epistle lesson is from Galatians, chapter 3, verses 23-29:
Now before faith came, we were held captive under the law, imprisoned until the coming faith would be revealed. So then, the law was our guardian until Christ came, in order that we might be justified by faith. But now that faith has come, we are no longer under a guardian, for in Christ Jesus you are all sons of God, through faith. For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. And if you are Christ’s, then you are Abraham’s offspring, heirs according to promise.
The Gospel for the Circumcision of Our Lord is from Luke, chapter 2, verse 21:
And at the end of eight days, when he was circumcised, he was called Jesus, the name given by the angel before he was conceived in the womb.

Circumcision, by Claudio Ridolfi [CC BY-SA 4.0]