God brought the Son of God into being "when the fullness of time had come, God sent forth his Son, born of a woman, born under the law to redeem those who were under the law, so that we might receive adoption as sons." (Gal. 4:4) "He was foreknown before the foundation of the world but was made manifest in the last times for the sake of you who through him are believers in God, who raised him from the dead and gave him glory, so that your faith and hope are in God." (1 Peter 1:20) He was known beforehand by God his Father and the Christ; the Messiah was prophesied about throughout the OT.
ALL scripture is God breathed, i.e. inspired by God and "knowing this first, that no prophecy of the scripture is of any private interpretation. For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Spirit.
God promised Jesus, "For you will not abandon my soul to Sheol, or let your holy one see corruption", therefore God raised him from the dead.
(Psalm 16:10)
God was with God in the beginning?
The God of Jesus is also our God; his Father also our Father - "Jesus said to her, "Do not cling to me, for I have not yet ascended to the Father; but go to my brothers and say to them, 'I am ascending to MY Father and YOUR Father, to MY God and YOUR God." (John 20:17)
Had I been a sincere Jew living during the times of Jesus then hopefully I would not have been like those unbelieving religious leaders who denied Christ but one of those in the group with Mary - Many of the Jews therefore, who had come with Mary and had seen what he did, believed in him (John 11:45) or the ones with Paul and James - "And when they heard it, they glorified God. And they said to him, "You see, brother, how many thousands there are among the Jews of those who have believed" (Acts 21:20) or the ones with Jesus - "So Jesus said to the Jews who had believed in him, 'If you abide in my word, you are truly my disciples'" (John 8:31) or the ones with Paul and Barnabus - "Now at Iconium they entered together into the Jewish synagogue and spoke in such a way that a great number of both Jews and Greeks believed."(Acts 14:1)