If one was in the habit of renting his house to others and found lost objects there, they belong to him.  

Normally, they should be returned to the last renter, but here we are dealing with a case of three people renting together. If one of them lost coins and can't find them, he despairs of getting them back. He thinks of the other two: “They probably took the coins and intend to keep them. But if I confront one, he can tell me that it was the other, and I can't make him to take an oath.” Thus the finder can keep them.