For as the Father hath life in himself; so hath he given to the Son to have life in himself;

Wesley's Notes

5:26 He hath given to the Son - By eternal generation, to have life in himself - Absolute, independent.

Jamieson-Fausset-Brown Bible Commentary

26. given to the Son, &c.-Does this refer to the essential life of the Son before all time (Joh 1:4) (as most of the Fathers, and Olshausen, Stier, Alford, &c., among the moderns), or to the purpose of God that this essential life should reside in the Person of the Incarnate Son, and be manifested thus to the world? [Calvin, Lucke, Luthardt, &c.] The question is as difficult as the subject is high. But as all that Christ says of His essential relation to the Father is intended to explain and exalt His mediatorial functions, so the one seems in our Lord's own mind and language mainly the starting-point of the other.

Matthew Henry's Concise Commentary

5:24-29 Our Lord declared his authority and character, as the Messiah. The time was come when the dead should hear his voice, as the Son of God, and live. Our Lord first refers to his raising those who were dead in sin, to newness of life, by the power of the Spirit, and then to his raising the dead in their graves. The office of Judge of all men, can only be exercised by one who has all knowledge, and almighty power. May we believe His testimony; thus our faith and hope will be in God, and we shall not come into condemnation. And may His voice reach the hearts of those dead in sin; that they may do works meet for repentance, and prepare for the solemn day.