Adam Clarke on John 16:10

Of righteousness - Of my innocence and holiness, because I go away to my Father; of which my resurrection from the dead, and my ascension to heaven, shall be complete proofs. Christ was treated by the Jews as an impostor; as a magician; as one possessed by the devil; as a wicked person, seducer, and destroyer of the law. His vindication from these charges he chiefly referred to the Holy Spirit, the Advocate, who, by his influences on the minds of the people, and by his eloquence and energy in the ministry of the apostles, convinced both the Jews and the Gentiles that the sentence of the Jewish rulers was unjust and infamous, and that the very person whom they had crucified was both Lord and Christ - Lord, the great governor of the universe; and Christ, the Lord's anointed, the promised Messiah. It was a matter of the utmost consequence to the Christian cause to have the innocence and holiness of its founder demonstrated, and the crime of the Jews in putting him to death made manifest to the world. This also has been literally fulfilled: the universe that has heard of him believes the righteousness and innocence of Jesus; and the Jews, his persecutors, are confounded and execrated throughout the habitable globe.