Numbers 15:38-40

Speak unto the children of Israel, and bid them that they make them tzitzit on the borders of their garments throughout their generations, and that they put upon the tzitzit of the borders a cord of blue: And it shall be unto you for a tzitzit, that you may look upon it, and remember all the commandments of YHWH, and do them; and that you follow not after your own heart and your own eyes, after which you used to go awhoring: That you may remember and do all My commandments, and be holy unto your Elohim.