Psalm 2:7, "I will tell of the decree: Yahweh said to Me, “You are my Son. Today I have become your Father"
Which, as can be seen from Herbrews 1:6, is speaking of the Incarnation of Jesus Christ, which is in the future
"For to which of the angels did he say at any time, “You are my Son. Today I have become your Father?” and again, “I will be to him a Father, and He will be to Me a Son?”
Isaiah 9:6, also confirms this, "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". These words in bold are in the future tense.
As does Luke 1:35, "And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God". Note, not IS "called", but the future tense, "κληθήσεται", SHALL BE CALLED, referring to the Birth of Jesus Christ.
John 1:1 does not say, "In the beginning was the Son, and the Son was with God, and the Son was God", which is the eternal relationship between the Father and Jesus Christ.
Likewise, in John 1:18, the reading with the strongest textual evidence reads, "No one has seen God at any time. The Unique God, who is in the bosom of the Father, has declared him.
Only in about 2 places Jesus Christ is referred to as "Son" in the Old Testament, as in Psalm 2:7, but always in Prophecy. We never read of the term, "God the Father" in the Old Testament.
The main description for Jesus Christ in the Old Testament, is "Malakh YHWH", which is often translated as "The Angel of Yahweh"; or "The Messenger of Yahweh"; Who, as can be seen from Exodus 3, is Himself "Yahweh", "Elohim" and "Ehyeh ’ăsher ’ehyeh". Showing Jesus' absolute equality with the Father and Holy Spirit!