TT #219 · Parashas Reeh · Fourth Aliyah · Passuk 14:21
You shall not eat any carcass; give it to the stranger within your gates, that he may eat it, or sell it to a foreigner; for you are a holy people to Hashem your God. You shall not boil a kid in its mother’s milk.
Torah Temimah points to Sifrei Devarim / Torah Temimah.
Sefaria — Torah Temimah on Deuteronomy 14:21
English: “For you are a holy people” — sanctify yourself in what is permitted to you; things that are permitted but others treat as forbidden, do not treat as permitted in their presence.
Derash on personal holiness (Sifrei / TT).
Holiness includes restraint even within the realm of the permitted.