2,164. Samson and Solomon - Part 3
Hilchos Issurei Biah 13:17
Let’s say that a court didn’t investigate a candidate for conversion, and they didn’t tell him about the mitzvos and the penalty for failing to observe them. If he was circumcised and immersed in front of three lay people, he is a convert. Even if it is later found that he converted for ulterior motives, since he was circumcised and converted, he has left the realm of non-Jews and we view him suspiciously until his righteousness is clear. If he later worships idols, he’s like an apostate Jew; if he betroths a woman, the betrothal is valid; it’s a mitzvah to return his lost property. Since he immersed, he became Jewish. This is why Samson and Solomon were able to keep their wives even though their insincerity in converting became known.
Hilchos Issurei Biah 13:18
This is why the Sages said that converts are as difficult for the Jewish people as a blemish of tzaraas (Yevamos 47a) – converts often go back to their old ways for some reason and this causes Jews to stray because it’s difficult to separate from them once they have joined the community. See, for example, what happened in the wilderness with the golden calf and the quail. Most of the incidents in which the Jews tried God were prompted by the mixed multitude.