Numbers 15:38-40

38“Speak to Bnei-Yisrael. Say to them that they are to make for themselves tzitzit on the corners of their garments throughout their generations, and they are to put a blue cord on each tzitzit.

39It will be your own tzitzit—so whenever you look at them, you will remember all the mitzvot of Adonai and do them and not go spying out after your own hearts and your own eyes, prostituting yourselves.

40This way you will remember and obey all My mitzvot and you will be holy to your God.