Numbers 15:37-41
And Hashem said to Moses saying: Speak to the Children of Israel and say to them that they are to make themselves tzitzis on the corners of their garments, throughout their generations. And they are to place upon the tzitzis of each corner a thread to techeiles. And it shall constitute tzitzis for you, that you may see it and remember all the commandments of Hashem and perform them; and not explore after your heart and after your eyes after which you stray. So that you may remember and perform all My commandments; and be holy to your G-d. I am Hashem, your G-d, Who has removed you from the land of Egypt to be a G-d to you.