And yet if I judge, my judgment is true: for I am not alone, but I and the Father that sent me.

Wesley's Notes

8:16 I am not alone - No more in judging, than in testifying: but I and the Father that sent me - His Father is in him, and he is in the Father, John 14:10,11; and so the Father is no more alone without the Son, than the Son is without the Father, Prov 8:22,23,30. His Father and he are not one and another God, but one God, (though distinct persons,) and so inseparable from each other. And though the Son came from the Father, to assume human nature, and perform his office as the Messiah upon earth, as God is sometimes said to come from heaven, for particular manifestations of himself; yet Christ did not leave the Father, nor the Father leave him, any more than God leaves heaven when he is said to come down to the earth.

Jamieson-Fausset-Brown Bible Commentary

16. And yet if I judge, my judgment is true, &c.-Ye not only form your carnal and warped judgments of Me, but are bent on carrying them into effect; I, though I form and utter My judgment of you, am not here to carry this into execution-that is reserved to a future day; yet the judgment I now pronounce and the witness I now bear is not Mine only as ye suppose, but His also that sent Me. (See on [1806]Joh 5:31, 32). And these are the two witnesses to any fact which your law requires.

Matthew Henry's Concise Commentary

8:12-16 Christ is the Light of the world. God is light, and Christ is the image of the invisible God. One sun enlightens the whole world; so does one Christ, and there needs no more. What a dark dungeon would the world be without the sun! So would it be without Jesus, by whom light came into the world. Those who follow Christ shall not walk in darkness. They shall not be left without the truths which are necessary to keep them from destroying error, and the directions in the way of duty, necessary to keep them from condemning sin.