Isa 9:6, Mt 1:21-23, Mt 3:16-17, Mt 17:4-5
In the Old Testament, the psalmist stated that only God and the Son of God ascended to heaven and then came down. (Proverbs 30:4)
Proverbs 30:4 Who hath ascended up into heaven, or descended? who hath gathered the wind in his fists? who hath bound the waters in a garment? who hath established all the ends of the earth? what is his name, and what is his son's name, if thou canst tell?
God has sent the Son of God to us. (Isa 9:6)
Isa 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
The Son of God has come to this earth. That is Jesus. (Matthew 1:21-23)
Matthew 1:21 And she shall bring forth a son, and thou shalt call his name Jesus: for he shall save his people from their sins. 22 Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, 23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
God Himself revealed that Jesus is the Son of God. (Mt 3:16-17, Mt 17:4-5)
Mt 3:16 And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him: 17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
Mt 17:4 Then answered Peter, and said unto Jesus, Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles; one for thee, and one for Moses, and one for Elias. 5 While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.