37 And יהוה spoke to Mosheh, saying,
38 Speak to the children of Yisra' el, and you shall say to them to make Tzitzit on the four corners of their garments throughout their generations, and to put a blue cord in the tzitzit of the corners.
39 And it shall be to you for a tzitzit and you shall see it, and shall remember all the commands of יהוה and shall do them, and not search after your own heart and your own eyes after which you went whoring,
40 so that you remember all my commands, and be set-apart unto your Elohim.
-Bemidbar 15: 37-40