We go back for everything that is meakev.
Shabbos 133b:
??? ?? ??? ???? ???? ????? ???? ??? ?? ?????? ??????? ?? ????? ??? ?? ?????? ???? ?????? ?? ????? ???? ?? ????? ??????? ?? ????? ???? ?? ????? ???? ?????? ?? ????? ???? ????
Rashi:
???. ????
Codified by Maran in the Beit Yosef and Shulchan Aruch Y.D. 266:2