Sayings Advocating Various Perversions or Sexual Corruptions

The Talmud Advocates for Incest:

§ The Sages taught: There is a case in which one performs ḥalitza with his mother due to uncertainty, or with his sister due to uncertainty, or with his daughter due to uncertainty. This is the halakha despite the fact that a levirate bond cannot be created between these relatives.

How so? If his mother and another woman had two sons, one each, and they then gave birth to two other sons in hiding, whose identities were confused, such that their lineage was consequently indeterminate, and the known son of this woman came and married the mother of that other known son, and the known son of that woman married this son’s mother, and they died without children, the halakha is that this one of the mixed sons performs ḥalitza with both women, as it is unknown which is his mother and which his yevama, and that one likewise performs ḥalitza with both women. It is therefore found that each one of them performs ḥalitza with his mother, due to the uncertainty. Yevamot 99a.1-2

Straining Out the Gnat:

The Gemara raises an objection from a baraita against the opinion that one who sins to express insolence is considered a heretic. The baraita teaches: If one ate a single flea or a single mosquito, he is considered an apostate. The Gemara clarifies the objection: But here it must be assumed that the insect was eaten to express insolence, as it is unappetizing, and yet this baraita teaches that one who eats a flea or a mosquito is an apostate. The Gemara answers: There, he desires to experience the taste of forbidden food, and therefore he is considered to be eating only due to temptation. - Avodah Zarah 26b.5