Mark 7:18
17 He said to them, “Are you so foolish? Don’t you understand that whatever goes into a person from outside cannot defile him? 18 For it does not enter his heart but his stomach, and then goes out into the sewer.” (This means all foods are clean.) 19 He said, “What comes out of a person defiles him.
Tosefta Oholot 12:3
ToseftaA se'ah measure overturned on the mouth of a barrel, or two domes placed one on top of the other, and a stone placed on top of the dome, bring impurity. A se'ah measure placed upright, a barrel placed upright, an inflated wineskin placed upright, a se'ah full of straw, a cushion full of feathers, or clothing full of handkerchiefs, two stones one on top of the other, or a dome on top of a stone, do not bring impurity. A dog that ate the flesh of a corpse and entered a house does not make the house impure, because anything swallowed by a person, an animal, a beast, or birds is pure. But if it vomits, the house becomes impure.
Notes and References
"... The reasoning of Galen and Aristotle, I think, is similar to the implicit reasoning of Mark’s Jesus in Mark 7:18–19. For Galen and Aristotle, the fact that food entering the body is qualitatively different from excrement that comes out of the body entails that the stomach enacts a qualitative change. For Mark’s Jesus, the fact that food entering the body – even if ritually contaminated by defiled hands – comes out of the body as ritually undefilable excrement entails that the stomach has a purifying effect on anything that enters it. We see precisely this kind of reasoning about purity, excrement, and the stomach in texts from the Tosefta. Tosefta Miqvaʾot 7:8–9 provides the following ruling ... A similar pattern of reasoning emerges in Tosefta Oholot 12:3 ... In the first passage, the corpse and impure liquids are made pure because, unlike something vomited up, that which is digested is ‘purified in the body’. Like Jesus’ argument, this view of the stomach arises from the assumption that excrement is impervious to impurity. Note also how the claim (appearing in both passages) that ‘everything that is swallowed by a human … is pure’ bears a striking resemblance to my proposed interpretation – the human body purifies any ingested food from ritual impurity ..."
Williams, Logan The Stomach Purifies All Foods: Jesus’ Anatomical Argument in Mark 7.18–19 (pp. 371-391) New Testament Studies, No. 70, 2024