Who said do unto others before they you and in what book?

There seems to be a slight misunderstanding in the statement you provided. The saying is actually, "Do unto others as you would have them do unto you," and it is often attributed to Jesus Christ in the Bible, specifically in the Gospel of Luke 6:31 (NIV):

"Do to others as you would have them do to you."

This teaching emphasizes treating others with the same kindness, respect, and fairness as we would want to be treated by them. It encourages empathy and reciprocity in relationships and interactions with others.