Machshirin 4:10-5:1

Machshirin 4:10

Let’s say that ritually unclean liquids fell on wood, followed by rain. If the rainwater exceeds the unclean liquids, the unclean liquids are rendered clean. If he took the wood outside so the rain would fall on it, then the liquids remain unclean even if the rainwater exceeds them. If the unclean liquids were absorbed within the wood, then even if he took the wood outside to be rained on, the rainwater remains clean. One may burn such wood in an oven only with ritually clean hands. Rabbi Shimon says that if the wood that absorbed the unclean liquids was still moist, then if the liquid exuded by the wood exceeds the liquid absorbed, they are clean.

Machshirin 5:1

Let’s say that a person immersed in a river and, on his way there, he passed through a different river. The water of the second river purifies the water from the first. If his drunk friend pushed him or his animal into the river (after he immersed), the second water purifies the first. If his friend pushed him into the river playfully, then ki yutan applies to it.