For as the Father has life in himself, so he has granted the Son also to have life in himself. - John 5:26
This Scripture is not explaining how Jesus the incarnation of the Word derives his life in a physical body. Of course all living things have God as the source of their life and without God nothing would live.
These all look to you, to give them their food in due season. When you give it to them, they gather it up; when you open your hand, they are filled with good things.
When you hide your face, they are dismayed; when you take away their breath, they die and return to their dust. When you send forth your Spirit, they are created, and you renew the face of the ground. - Psalm 104:27-30
But Jesus is revealing here that the same kind of life that the Father has in Himself, eternal self-existent life, has been granted also for the Son to have in Himself. As the Father does not need to draw upon an external source in order for Him to perpetuate His own life, so it is with the Son and so it always has been.
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through him, and without him was not any thing made that was made. In him was life, and the life was the light of men. - John 1:1-4
And as the Father can choose to be the external source of life for whomever He chooses, so also the Son can give life to whomever He chooses.
For as the Father raises the dead and gives them life, so also the Son gives life to whom he will. - John 5:21
Just as the living Father sent me and I live because of the Father, so the one who feeds on me will live because of me. - John 6:57
It has always been this way. The Triune God created all things and all life is sourced in Him; both temporal life and eternal life. Nothing temporal has been created without the Son (John 1:3) and no eternal life is possible without the Son.
And this is the testimony, that God gave us eternal life, and this life is in his Son. Whoever has the Son has life; whoever does not have the Son of God does not have life. - 1 John 5:11-12
The Word (logos) that was made into flesh is the Divine Mind, not just the Word but the thought and intent behind the Word. As it is impossible to conceive of the Divine Mind existing apart from the Divine Being, so it is impossible to conceive of the Son existing apart from the Father. As it is impossible to conceive of the Divine Being apart from the Divine Mind (a mindless God), so it is impossible to conceive of the Father without the Son.
There is much confusion reconciling the Trinity with the Son's subordinate role to the Father and it is cleared up in this way. There is no ontological difference between the infinite, eternal mind of an infinite, eternal being and the infinite, eternal being itself if that being has perfect integrity. The thought (Logos) always proceeds from the being and never the being from the thought. The Divine Mind is subordinate in role but not less than ontologically.
The early church writers were accurate when they described the Son as eternally begotten of the Father. Jesus lives because of the Father but, as He is the incarnation of the eternal, infinite Divine Mind, He is not less than.