Matthew Poole and continuators on John 5:26

26 For as the Father hath life in himself, so hath he given to the Son to have life in himself .

How the Eternal Father hath Life in himself, is obvious to every Capacity; for he is the first mover, and therefore must have his Life in, and from himself, and not from any other: And he is the first cause, and therefore that Life which floweth from him to all Created Beings, must first be in him, as in its Fountain. But in what sense it is said, that he hath given to the Son to have life in himself; whether as God, by his Eternal Generation, or as the Messiah and Mediator betwixt God and Man; and so the Fountain of Spiritual Life to Believers is more questioned. Those who understand it, as to the Divine Nature, say, that this Phrase [hath life in himself] is expressive of the name Iehovah; and that Christ is proved to be the true Iehovah, by what is here said, that he hath life in himself. But they distinguish betwixt having life from, or by himself, and having life in himself. The Text saith, It is given to Christ to have Life in himself. But there are other Interpreters, who seem better to understand it of Christ as Mediator, to whom it is given to have Life in himself, to communicate to his Creatures; and think it is well Interpreted by Ch. 1.4. In him was life, and the life was the light of men.