no man - namely, to atone by his righteousness for the unrighteousness of the people. “Man” is emphatic, as in 1Ki 2:2; no representative man able to retrieve the cause of fallen men (Isa 41:28; Isa 63:5, Isa 63:6; Jer 5:1; Eze 22:30).
no intercessor - no one to interpose, “to help ... uphold” (Isa 63:5).
his arm - (Isa 40:10; Isa 51:5). Not man’s arm, but His alone (Psa 98:1; Psa 44:3).
his righteousness - the “arm” of Messiah. He won the victory for us, not by mere might as God, but by His invincible righteousness, as man having “the Spirit without measure” (Isa 11:5; Isa 42:6, Isa 42:21; Isa 51:8; Isa 53:11; 1Jo 2:1).