C. F. Keil and Franz Delitzsch on Numbers 15:37-38

Num 15:37-38 (cf. Deu 22:12). The command to wear Tassels on the Edge of the Upper Garment appears to have been occasioned by the incident just described. The Israelites were to wear ציצת, tassels, on the wings of their upper garments, or, according to Deu 22:12, at the four corners of the upper garment. כּסוּת, the covering in which a man wraps himself, synonymous with בּגד, was the upper garment, consisting of a four-cornered cloth or piece of stuff, which was thrown over the body-coat (see my Bibl. Archäol. ii. pp. 36, 37), and is not to be referred, as Schultz supposes, to the bed-coverings also, although this garment was actually used as a counterpane by the poor (see Exo 22:25-26). “And upon the tassel of the wing they shall put a string of hyacinth-blue,” namely, to fasten the tassel to the edge of the garment. ציצת (fem., from ציץ, the glittering, the bloom or flower) signifies something flowery or bloom-like, and is used in Eze 8:3 for a lock of hair; here it is applied to a tassel, as being made of twisted threads: lxx κράσπεδα; Mat 23:5, “borders.” The size of these tassels is not prescribed. The Pharisees liked to make them large, to exhibit openly their punctilious fulfilment of the law. For the Rabbinical directions how to make them, see Carpzov. apparat. pp. 197ff.; and Bodenschatz, kirchliche Verfassung der heutigen Juden, iv. pp. 11ff.