2,159. An Invalid Conversion

Hilchos Issurei Biah 13:7

A minor who wants to convert is immersed based on the court’s approval because it’s an advantage for him. If a pregnant woman converts and immerses in a mikvah, her child doesn’t need to be immersed separately. If a convert immerses and converts alone, or even if he does so in front of two witnesses, the conversion is invalid. If someone claims to have converted in a certain court, his word is not accepted when it comes to marrying Jews until he brings witnesses.

Hilchos Issurei Biah 13:8

Let’s say that he was married to a woman who was born Jewish or to a convert and they already had children together. If he claims to have converted alone, he is taken at his word to disqualify himself but not to disqualify his children. He must immerse again in the front of a court.