Everything creeping thing that crawls on the ground is detestable; do not eat it (Leviticus 11:41)
Having completed its detour into some areas of ritual impurity, the Torah now returns to this chapter’s main topic: kosher and non-kosher animals. Here, we are told that we may not eat anything that crawls on the ground, whether it slithers (like a snake), has four legs (like a lizard), or many legs (like a centipede). God is especially emphatic here, telling us “do not make yourselves detestable” as a consequence of eating them.
It is prohibited to eat any amount of such creeping things, though the minimum amount to incur a penalty depends on the type of creature. For most of these, it would take an olive-sized piece to make someone liable for punishment. In the case of the eight sheratzim that impart ritual impurity (see Mitzvah #159), one would be liable even for eating a lentil-sized piece (the same size that is capable of rendering one impure).
This mitzvah applies to both men and women in all times and places. It is discussed in the Talmud in tractate Chulin (see, for example, pages 67a-b) and in Meilah (16a-17b). It is codified in the Shulchan Aruch in Yoreh Deah 84. It is #176 of the 365 negative mitzvos in the Rambam’s Sefer HaMitzvos and #97 of the 194 negative mitzvos that can be fulfilled today as listed in the Chofetz Chaim’s Sefer HaMitzvos HaKatzar.