From where do we learn that a woman who emits semen on the third day is tamei? For it is stated: Be prepared for three days (Exodus 19:15). From where do we learn that we may bathe a circumcised infant on the third day [even] if it falls on the Sabbath? For it is stated: And it came to pass on the third day when they were in pain (Genesis 34:25). From where do we learn that a strip of red wool is tied on the head of the goat that is sent out? For it is stated: If your sins will be like crimson, they will become white as snow (Isaiah 1:18).