“Whilst remaining pre-existent, He begins to exist in time. The Lord of the universe veiled His measureless majesty and took on a servant’s form. The God who knew no suffering did not despise becoming a suffering man, and, deathless as He is, to be subject to the laws of death.”
Pope Saint Leo the Great
“Whilst remaining pre-existent, He begins to exist in time.” This is the finest definition of the infinity of God. God is. Does God exist? Yes, in the Person of Jesus Christ, God exists in time and space.
The three Persons of the Supreme Sovereign Being are pre-existent, while Jesus Christ is true God and true Man before all ages in the Hypostatic Union, the union of divine and human natures in the single person of Christ.