50:4-9 As Jesus was God and man in one person, we find him sometimes speaking, or spoken of, as the Lord God; at other times, as man and the servant of Jehovah. He was to declare the truths which comfort the broken, contrite heart, those weary of sin, harassed with afflictions. And as the Holy Spirit was upon him, that he might speak as never man spake; so the same Divine influence daily wakened him to pray, to preach the gospel, and to receive and deliver the whole will of the Father. The Father justified the Son when he accepted the satisfaction he made for the sin of man. Christ speaks in the name of all believers. Who dares to be an enemy to those unto whom he is a Friend? or who will contend with those whom he is an Advocate? Thus St. Paul applies it, Ro 8:33.
5. opened … ear—(See on Isa 42:20; Isa 48:8); that is, hath made me obediently attentive (but Maurer, "hath informed me of my duty"), as a servant to his master (compare Ps 40:6-8, with Php 2:7; Isa 42:1; 49:3, 6; 52:13; 53:11; Mt 20:28; Lu 22:27).
not rebellious—but, on the contrary, most willing to do the Father's will in proclaiming and procuring salvation for man, at the cost of His own sufferings (Heb 10:5-10).