Jamieson, Fausset and Brown on Isaiah 42:6

6. in righteousness--rather, "for a righteous purpose" [Lowth]. (See Is 42:21). God "set forth" His Son "to be a propitiation (so as) to declare His (God's) righteousness, that God might be just, and (yet) the justifier of him which believeth in Jesus" (Ro 3:25, 26; compare see on Is 41:2; Is 45:13; 50:8, 9).

hold ... hand--compare as to Israel, the type of Messiah, Ho 11:3.

covenant--the medium of the covenant, originally made between God and Abraham (Is 49:8). "The mediator of a better covenant" (He 8:6) than the law (see Is 49:8; Jr 31:33; 50:5). So the abstract "peace," for peace-maker (Mi 5:5; Ep 2:14).

the people--Israel; as Is 49:8, compared with Is 42:6, proves (Lu 2:32).