Jamieson, Fausset and Brown on Isaiah 61:2

2. acceptable year--the year of jubilee on which "liberty was proclaimed to the captives" (Is 61:1; 2Co 6:2).

day of vengeance--The "acceptable time of grace" is a "year"; the time of "vengeance" but "a day" (so Is 34:8; 63:4; Mal 4:1). Jesus (Lu 4:20, 21) "closed the book" before this clause; for the interval from His first to His second coming is "the acceptable year"; the day of vengeance" will not be till He comes again (2Th 1:7-9).

our God--The saints call Him "our God"; for He cometh to "avenge" them (Re 6:10; 19:2).

all that mourn--The "all" seems to include the spiritual Israelite mourners, as well as the literal, who are in Is 61:3 called "them that mourn in Zion," and to whom Is 57:18 refers.