St. Thomas Aquinas, Summa Theologica: “On the contrary, It is written (Luke 2:21): ‘After eight days were accomplished, that the child should be circumcised.’ I answer that, For several reasons Christ ought to have been circumcised. First, in order to prove the reality of His human nature, in contradiction to the Manicheans, who said that He had an imaginary body: and in contradiction to Apollinarius, who said that Christ’s body was consubstantial with His Godhead; and in contradiction to Valentine, who said that Christ brought His body from heaven. Secondly, in order to show His approval of circumcision, which God had instituted of old. Thirdly, in order to prove that He was descended from Abraham, who had received the commandment of circumcision as a sign of his faith in Him. Fourthly, in order to take away from the Jews an excuse for not receiving Him, if He were uncircumcised. Fifthly, ‘in order by His example to exhort us to be obedient’ [Bede, Hom. x in Evang.]. Wherefore He was circumcised on the eighth day according to the prescription of the Law (Leviticus 12:3). Sixthly, ‘that He who had come in the likeness of sinful flesh might not reject the remedy whereby sinful flesh was wont to be healed.’ Seventhly, that by taking on Himself the burden of the Law, He might set others free therefrom, according to Galatians 4:4-5: ‘God sent His Son . . . made under the Law, that He might redeem them who were under the Law. ...Reply to Objection 2. ...Moreover, according to Origen (Hom. xiv in Luc.), ‘as we died when He died, and rose again when Christ rose from the dead, so were we circumcised spiritually through Christ: wherefore we need no carnal circumcision.’ And this is what the Apostle says (Colossians 2:11): "In whom," [i.e. Christ] ‘you are circumcised with circumcision not made by hand in despoiling of the body of the flesh, but in the circumcision of’ our Lord Jesus ‘Christ.’ Reply to Objection 3. As Christ voluntarily took upon Himself our death, which is the effect of sin, whereas He had no sin Himself, in order to deliver us from death, and to make us to die spiritually unto sin, so also He took upon Himself circumcision, which was a remedy against original sin, whereas He contracted no original sin, in order to deliver us from the yoke of the Law, and to accomplish a spiritual circumcision in us—in order, that is to say, that, by taking upon Himself the shadow, He might accomplish the reality.”

“On the contrary is the authority of Scripture, in which it is written (Luke 2:21): ‘After eight days were accomplished, that the child should be circumcised, His name was called Jesus.’ I answer that, A name should answer to the nature of a thing. This is clear in the names of genera and species, as stated Metaph. iv: ‘Since a name is but an expression of the definition’ which designates a thing’s proper nature. Now, the names of individual men are always taken from some property of the men to whom they are given. Either in regard to time; thus men are named after the Saints on whose feasts they are born: or in respect of some blood relation; thus a son is named after his father or some other relation; and thus the kinsfolk of John the Baptist wished to call him ‘by his father’s name Zachary,’ not by the name John, because ‘there’ was ‘none of’ his ‘kindred that’ was ‘called by this name,’ as related Luke 1:59-61. Or, again, from some occurrence; thus Joseph ‘called the name of’ the ‘first-born Manasses, saying: God hath made me to forget all my labors’ (Genesis 41:51). Or, again, from some quality of the person who receives the name; thus it is written (Genesis 25:25) that ‘he that came forth first was red and hairy like a skin; and his name was called Esau,’ which is interpreted ‘red.’ But names given to men by God always signify some gratuitous gift bestowed on them by Him; thus it was said to Abraham (Genesis 17:5): ‘Thou shalt be called Abraham; because I have made thee a father of many nations’: and it was said to Peter (Matthew 16:18): ‘Thou art Peter, and upon this rock I will build My Church.’ Since, therefore, this prerogative of grace was bestowed on the Man Christ that through Him all men might be saved, therefore He was becomingly named Jesus, i.e. Saviour: the angel having foretold this name not only to His Mother, but also to Joseph, who was to be his foster-father. Reply to Objection 1. All these names in some way mean the same as Jesus, which means ‘salvation.’ For the name ‘Emmanuel, which being interpreted is ‘God with us,’ designates the cause of Salvation, which is the union of the Divine and human natures in the Person of the Son of God, the result of which union was that ‘God is with us.’ When it was said, ‘Call his name, Hasten to take away,’ etc., these words indicate from what He saved us, viz. from the devil, whose spoils He took away, according to Colossians 2:15: ‘Despoiling the principalities and powers, He hath exposed them confidently.’ When it was said, ‘His name shall be called Wonderful,’ etc., the way and term of our salvation are pointed out: inasmuch as ‘by the wonderful counsel and might of the Godhead we are brought to the inheritance of the life to come,’ in which the children of God will enjoy ‘perfect peace’ under ‘God their Prince.’ When it was said, ‘Behold a Man, the Orient is His name,’ reference is made to the same, as in the first, viz. to the mystery of the Incarnation, by reason of which ‘to the righteous a light is risen up in darkness’ (Psalm 111:4).

Reply to Objection 2. The name Jesus could be suitable for some other reason to those who lived before Christ—for instance, because they were saviors in a particular and temporal sense. But in the sense of spiritual and universal salvation, this name is proper to Christ, and thus it is called a ‘new’ name.