004.171 O People of the Book! Commit no excesses in your religion: Nor say of Allah aught but the truth. Christ Jesus the son of Mary was an Apostle of Allah, and His Word, which He bestowed on Mary, and a Spirit proceeding from Him: so believe in God and His Messengers. Say not "three [gods]" : desist: it will be better for you: for God is One God: Glory be to Him: above having a son [truly the Glory seen in His Son Jesus Christ but not in the pagan sense of earthly begetting of false gods such as Zeus and Leto]. To Him belong all things in the heavens and on earth. And enough is God as a Disposer of affairs.
See these Biblical verses in agreement with the above Ayat 171 of Surah 4.
Hebrews 3:1 Wherefore, holy brethren, partakers of the heavenly vocation, consider the Apostle and High Priest of our confession, Jesus:
John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. 2 The same was in the beginning with God. 3 All things were made by him: and without him was made nothing that was made. 4 In him was life, and the life was the light of men.
2 Cor. 3:17 Now the Lord is a Spirit. And where the Spirit of the Lord is, there is liberty. 18But we all beholding the Glory of the Lord [Jesus Christ] with open face, are transformed into the same image from glory to glory, as by the Spirit of the Lord.
Apostle is the One who comes forth from God, in this case Jesus Christ the Messiah Himself, born of the Holy Spirit and the blessed virgin Mary, as both Christian truth and Islam teach.
He is the pre-existent Word of God through whom all things were created.
And through the Messiah Jesus Christ alone is the gift of the Holy Spirit of God to all who believe in Him.
This verse from the Gospel (Injil of John) of says it - John 3:13 And no man hath ascended into heaven, but he that descended from heaven, the Son of man who is in heaven.
He came forth, therefore the Apostle of God, the Word descended from heaven and became Incarnate of the Holy Spirit and the blessed virgin Mary, hence He is the Son of man - Incarnate from the flesh of Mary by the Holy Spirit, while remaining the Son of God (that is the pre-existent Word of God) now Incarnate, the son of Mary.
Therefore the heavenly host sang at His birth -
Luke 2:11 For, this day, is born to you a Saviour, who is Christ the Lord, in the city of David. 12 And this shall be a sign unto you. You shall find the infant wrapped in swaddling clothes, and laid in a manger. 13 And suddenly there was with the angel a multitude of the heavenly army, praising God, and saying: 14 Glory to God in the highest; and on earth peace to men of good will.
Notice the blessing that is upon the Christ Child and in Him and through Him on all of good will - peace. Therefore the blessing of Muslims upon Christ and His mother and the prophet of PBUH. Peace be upon him/her.