For the Lord God will help me,.... As he promised he would, and did, Psalm 89:21, which is no contradiction to the deity of Christ, nor any suggestion of weakness in him; for he is the true God, and has all divine perfections in him; is equal to his Father in power, as well as in glory, and therefore equal to the work of redemption, as his other works show him to be; but this is to be understood of him as man, and expresses his strong faith and confidence in God, and in his promises as such; and in his human nature he was weak, and was crucified through weakness, and in it he was made strong by the Lord, and was held and upheld by him: and this shows the greatness of the work of man's redemption, that it was such that no mere creature could effect; even Christ as man needed help and assistance in it; and also the concern that all the divine Persons had in it:

continued...

But no shame makes him faint-hearted; he trusts in Him who hath called him, and looks to the end. "But the Lord Jehovah will help me; therefore have I not suffered myself to be overcome by mockery: therefore did I make my face like the flint, and knew that I should not be put to shame." The ו introduces the thought with which his soul was filled amidst all his sufferings. In נכלמתּי לא he affirms, that he did not suffer himself to be inwardly overcome and overpowered by kelimmâh. The consciousness of his high calling remained undisturbed; he was never ashamed of that, nor did he turn away from it. The two על־כּן stand side by side upon the same line. He made his face kachallâmı̄sh (from châlam, related to gâlam in Isaiah 49:21, with the substantive termination ı̄sh: see Jeshurun, p. 229), i.e., he made it as unfelling as a flint-stone to the attacks of his foes (cf., Ezekiel 3:8-9). The lxx renders this ἔθηκα τὸ πρόσωπον μου ὡς στερεὰν πέτραν; but ἐστήριξα τὸ πρός, which is the rendering given to פני שׂים in Jeremiah 21:10, would have been just the proper rendering here (see Luke 9:51). In "holy hardness of endurance," as Stier says, he turned his face to his antagonists, without being subdued or frightened away, and was well assured that He whose cause he represented would never leave him in the lurch.

For the Lord God will help me - That is, he will sustain me amidst all these expressions of contempt and scorn.

continued...

Therefore have I set my face like a flint - The Prophet Ezekiel, Ezekiel 2:8, Ezekiel 2:9, has expressed this with great force in his bold and vehement manner:

continued...

For the Lord GOD will help me; therefore shall I not be confounded: therefore have I set my face like a flint, and I know that I shall not be ashamed.

7. Sample of His not being "discouraged" (Isa 42:4; 49:5).

set … face like … flint-set Myself resolutely, not to be daunted from My work of love by shame or suffering (Eze 3:8, 9).

Isaiah 50:7 Parallel Commentaries
Bible Hub: Online Parallel Bible