Jamieson, Fausset and Brown on Isaiah 42:4

4. fail--faint; man in religion may become as the almost expiring flax-wick (Is 42:3), but not so He in His purposes of grace.

discouraged--literally, "broken," that is, checked in zeal by discouragements (compare Is 49:4, 5). Rosenmuller not so well translates, "He shall not be too slow on the one hand, nor run too hastily on the other."

judgment--His true religion, the canon of His judgments and righteous reign.

isles ... wait, &c.--The distant lands beyond sea shall put their trust in His gospel way of salvation. Mt 12:21 virtually gives the sense, with the inspired addition of another aspect of the same thing, "In his name shall the Gentiles trust" (as "wait for" here means, Is 30:18). "His law" is not something distinct from Himself, but is indeed Himself, the manifestation of God's character ("name") in Christ, who is the embodiment of the law (Is 42:21; Jr 23:6; Ro 10:4). "Isles" here, and in Is 42:12, may refer to the fact that the populations of which the Church was primarily formed were Gentiles of the countries bordering on the Mediterranean.