I am the one who bears witness about myself, and the Father who sent me bears witness about me.”
The rest of the chapter is taken up with debates between Christ and contradicting sinners, who cavilled at the most gracious words that proceeded out of his mouth. It is not certain whether these disputes were the same day that the adulteress was discharged; it is probable they were, for the evangelist mentions no other day, and takes notice (Joh 8:2) how early Christ began that day's work.
Commenting on John 8:12-20
These words spake Jesus in the treasury,.... The place where the thirteen chests stood, into which the people put their voluntary contributions for the sacrifices, and service of the temple: the Ethiopic version renders it, "at the alms chest"; See Gill on Mar 12:41.
Verse 18. I am one that bear witness of myself. In human courts a man is not allowed to bear witness of himself, because he has a personal interest in the case, and the court could have no proof of the impartiality of the evidence; but in the case of Jesus it was otherwise.