Psalms 2:7b

Thou art my Son, this day have I begotten thee.

'This day' suggest an exact day the second person in the Trinity became the only begotten Son of God.

Before his incarnation where he took the human body to redeem mankind, the second person in the Trinity was not the son the God. He was called others names like Lord (The Lord Said to my Lord), Messiah.

It was at his incarnation, God had a son through Mary's virgin Birth. This happened at a certain day.... 'This day' about 2020 years ago.

God the Father didn't have a Son before 'This day'. The son of God refers to Christ's humanity not his deity.

As God, the person we now know of as Jesus Christ had no beginning, was not begotten, was not a son and did not come into being. He always existed as God as was Still God even while in the flesh(remember He received worship while on earth as God).

But as Man and as God's son, he was not eternal, with a beginning and became the Begotten son of God.

The second person only became the Son of God on 'this day', the day He was begotten, the day he was born.

Amen.

We're u there