Numbers 15:37-40

And the Lord said to Moses, Say to the children of Israel that through all their generations they are to put on the edges of their robes an ornament of twisted threads, and in every ornament a blue cord; So that, looking on these ornaments, you may keep in mind the orders of the Lord and do them; and not be guided by the desires of your hearts and eyes, through which you have been untrue to me: And that you may keep in mind all my orders and do them and be holy to your God.