Taken from MacArthur study Bible.
Repent. This is no mere academic change of mind, nor mere regret or remorse. John the Baptist spoke of repentance as a radical turning from sin that inevitably became manifest in the fruit of righteousness (v. 8 ). Jesus’ first sermon began with the same imperative ( 4:17 ). For a discussion of the nature of repentance, see notes on 2Co 7:8–11
Repentance itself is not a work, but works are its inevitable fruit. Repentance and faith are inextricably linked in Scripture. Repentance means turning from one’s sin, and faith is turning to God (cf. 1Th. 1:9 ). They are like opposite sides of the same coin. That is why both are linked to conversion ( Mk 1:15 ; Ac 3:19 ; 20:21 ). Note that the works John demanded to see were “fruit” of repentance. But repentance itself is no more a “work” than faith is ( see note on 2Ti 2:25