Numbers 15:38-39

38“Speak to the sons of Israel and tell them to make for themselves tassels on the hems of their garments throughout their generations, and put a cord of blue on the tassel of each hem.

39It shall be a tassel for you to look at and remember all the commandments of the Lord, to do them, so that you do not follow after [the desires of] your own heart and eyes, [desires] after which you used to follow and play the prostitute,