thou - who dost wish to be a true descendant of Jacob.
to thy God - who is therefore bound by covenant to hear thy prayers.
keep mercy and judgment - (Mic 6:8). These two include the second-table commandments, duty towards one’s neighbor, the most visible test of the sincerity on one’s repentance.
wait on thy God - alone, not on thy idols. Including all the duties of the first table (Psa 37:3, Psa 37:5, Psa 37:7; Psa 40:1).