NUM71 R. Dostai expounded: And when it rested, he said"" -- This teaches us that the Shechinah does not rest upon fewer than two thousand and two ten thousands of Israel. So that if Israel were two thousand and two ten thousands less one, and there were a pregnant woman among them, who could complete the number, and a dog barked at her and caused her to miscarry -- it would emerge that this one [the owner of the dog] had caused the Shechinah to depart from Israel -- whence it was ruled: One may not keep a dog unless it is chained (Bava Kamma 83b)