So, what did Jesus' circumcision accomplish for Him?
It marked him as a descendant of Abraham and an heir of the promises God made to him. It united him with God's chosen people, so that ultimately he would unite all of God's chosen people from all nations in himself.
Did it remove the stain of Adam's sin from Him?
As part of the Great Exchange, Christ who had no sin was circumcised into our sinful flesh, under the law, so that in Christ our flesh would be circumcised unto God through the law of grace.
2 Corinthians 5:21
For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God.
Jesus was circumcised for the precisely same reason that he was baptized by St John the Baptizer - in order to unite his sinless self with sinful mankind to bear our sins in his body to death on the cross, in order to fulfill all righteousness for us, not for him.
The link between circumcision and baptism is very strong, leading St Paul to refer to Christian baptism as the circumcision of the heart, the circumcision not made by hands.
Did it make Him any more God than He had been at birth?
Is God circumcised? Circumcision was the sign and seal of the Abrahamic covenant. It didn't make him
more God but it did make him
more Israel, and
more THAN Israel, as the ultimate and true heir of the promises of God.
Did it prove to God that He was obedient?
Yes, this was also part of the reason. It was part of his perfect active obedience to the law of God, both proving and preserving his unique status as the Lamb of God who takes away the sins of the world.
These are really good questions,
@bbbbbbb. Thanks for making me stop and think. Here are some of the other passages I looked at to address them. Also see here:
SUMMA THEOLOGIAE: Christ's circumcision, and of the other legal observances accomplished in regard to the child Christ (Tertia Pars, Q. 37) for an interesting exposition.
Matthew 5:17-20
“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. Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven.
Galatians 4:4-7
But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. And because you are sons, God has sent the Spirit of his Son into our hearts, crying, “Abba! Father!” So you are no longer a slave, but a son, and if a son, then an heir through God.
Colossians 2:8-15
See to it that no one takes you captive by philosophy and empty deceit, according to human tradition, according to the elemental spirits of the world, and not according to Christ. For in him the whole fullness of deity dwells bodily, and you have been filled in him, who is the head of all rule and authority. In him also you were circumcised with a circumcision made without hands, by putting off the body of the flesh, by the circumcision of Christ, having been buried with him in baptism, in which you were also raised with him through faith in the powerful working of God, who raised him from the dead. And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. He disarmed the rulers and authorities and put them to open shame, by triumphing over them in him.
Romans 2:25-29
For circumcision indeed is of value if you obey the law, but if you break the law, your circumcision becomes uncircumcision. So, if a man who is uncircumcised keeps the precepts of the law, will not his uncircumcision be regarded as circumcision? Then he who is physically uncircumcised but keeps the law will condemn you who have the written code and circumcision but break the law. For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter. His praise is not from man but from God.
Romans 5:19
For as by the one man’s disobedience the many were made sinners, so by the one man’s obedience the many will be made righteous.
Hebrews 5:5-10
So also Christ did not exalt himself to be made a high priest, but was appointed by him who said to him,
“You are my Son,
today I have begotten you”;
as he says also in another place,
“You are a priest forever,
after the order of Melchizedek.”
In the days of his flesh, Jesus offered up prayers and supplications, with loud cries and tears, to him who was able to save him from death, and he was heard because of his reverence. Although he was a son, he learned obedience through what he suffered. And being made perfect, he became the source of eternal salvation to all who obey him, being designated by God a high priest after the order of Melchizedek.