Behold, I have given him, &c.— The witness and leader here spoken of, unquestionably, is the Messiah, whom God declares that he had given, not to instruct the Jews only, but also the people of the Gentiles. Instead of commander, Vitringa reads instructor. Christ is the faithful and true witness. See Revelation 3:14.
Related Commentaries of Isaiah 55:4
Isaiah 55:4
4 Behold, I have given him for a witness to the people, a leader and commander to the people.