Isaiah 42:4

לֹא יִכְהֶה וְלֹא יָרוּץ עַד־יָשִׂים בָּאָרֶץ מִשְׁפָּט וּלְתוֹרָתוֹ אִיִּים יְיַחֵלוּ׃

4 He will not fail, he will not be crushed until he has established justice in the land. And the islands wait for his Lord.

לֹא יִכְהֶה וְלֹא יָרוּץ He will not fail, he will not be crushed, יִכְהֶה is the verbal form of כֵהָה "fail, grow dim." In the same way, יָרוּץ is the qal imperfect of רָצַץ "crush." The variant reading of the LXX θραυσθρήσεται (future passive ind, 3rd sg from θραύω "oppress," cf. Luke 4:18) is more an interpretation rather than a reading of the Hebrew text. The things that the Lord will not do to the weak and the very things that describe the weak are things that the Lord will neither do nor be.

עַד־יָשִׂים בָּאָרֶץ מִשְׁפָּט until he has established justice in the land. יָשִׂים is the qal imperfect of שִׂים. Here עַד means "up to the point of." It doesn't imply that the Savior will be able to fail after his task is complete (as the English "until" could imply), but that failure is not a possibility, right through to the completion of his task.

וּלְתוֹרָתוֹ אִיִּים יְיַחֵלוּ And the islands wait for his law. יְיַחֵלוּ is the piel imperfect (note the shewa under the prefixed yod) from יָחַל, "hope, wait expectantly." In what sense is this hopeful wait? It can be both retrospective (the Gentiles also put their hope in him) or prospective (anticipating the salvation of the Gentiles). In Isaiah אִיִּים "islands" is an important term, calling our attention out beyond the shoreline of Canaan to the farthest reaches of the earth. All of the Gentiles are also the object of God's loving concern, and the gospel must reach out to them, too.

Verse 4 concludes the quote from the Lord's courtroom that was begun in 41:25 (note the פ paragraph marker). Jesus brought justice and peace into the world through his own body; through his own suffering and death. The people trust in him because he has put faith in their hearts: “I have not departed from your laws, for you yourself have taught me” (Psalm 119:102)