Deuteronomy 14:21

Ver. 21. Ye shall not eat of any thing that dieth of itself— To this discourse about food it was proper to add a caution, that though they might kill and eat any clean creature, yet, if it died of itself, it was unlawful to eat it, because the blood was in it. Proselytes of the gate, who were not obliged to observe these laws, or mere Gentiles who might happen to be in their country, might eat such food; but as to those who were called proselytes of righteousness, i.e. circumcised Gentiles, who had embraced the Jewish religion, they were obliged to abstain from such food as much as the native Jews. The Egyptians, in the same manner, sold to others what they might not eat themselves. So Herodotus tells us, that they first imprecated many curses upon the head of the victim, and then carried it to those who trafficked with the Greek merchants, that they might sell it to them; but, if no such Greeks were there, they cast it into the river.