Adam Clarke on John 15:25

Written in their law - See on Joh 10:34 (note). These words are taken from Psa 69:4. This psalm is applied to Christ, Joh 2:17; Joh 19:28; to the vengeance of God against Judea, Act 1:20. The psalm seems entirely prophetic of Christ. His deep abasement is referred to, Psa 69:2-5; his prayer for his disciples and followers, Psa 69:6; that for himself, in the garden of Gethsemane, Psa 69:15-19; his crucifixion, Psa 69:20-22; the vengeance of God against the Jews, from Psa 69:23-29; the glorious manner in which he gets out of all his sufferings, Psa 69:30; the abolition of the Mosaic rites and ceremonies, Psa 69:31, compared with Isa 66:3; and, finally, the establishment of the Gospel through the whole world, in Psa 69:33 and following verses. The reader will do well to consult the psalm before he proceeds.