On December 25th, the Christians celebrate the birth of their God, Jesus, the Son of God. The Christians worship the Father, the Son (Jesus), and the Holy Spirit as their God.
In Islam, we worship one God only, namely Allah, and no one else. In fact, Islam regards Jesus as one of the messengers of God just like Adam, Moses, Abraham, Isaac, and Muhammad:
“We gave Moses the Book and followed him up with a succession of Messengers; We gave Jesus, the son of Mary, Clear (Signs) and strengthened him with the Holy Spirit. Is it that whenever there comes to you a Messenger with what ye yourselves desire not, ye are puffed up with pride” Some ye called impostors, and others ye slay!” [Al Baqarah:87]