If you are born into a Jewish family (both parents), and you leave Judaism for other religions that include their rites of joining (baptism), then decide to come back to Judaism, do you need to do anything more than come back to a congregation? Is there a ritual or something similar involved?

Answer

A conversion to another religion is ineffective. According to Jewish law, a person is always Jewish - regardless of whether they reject their heritage, ignore it, or practice another religion.

Technically, nothing is necessary to return to Jewish life, although it is customary to undergo a dipping in the mikveh (ritual bath) to symbolize one's return.