Rashi explains how the tzitzis fringes remind us of all the mitzvos. The numerical equivalents of the letters that spell the word tzitzis, ציצית, total 600. Add 8 for the number of threads on each corner, 5 for the number of knots tied on each fringe, and you have 613. The sight of the tzitzis thus reminds us of the 613 commandments.Yet if the fringes alone remind us of the mitzvos, why does the fulfillment of this mitzvah require that the fringes be attached to a garment, a tallis? This requirement indicates that there is more to remembering the mitzvos than calling to mind the number 613.

Unlike food that becomes absorbed in our flesh and blood, the clothing we wear envelops us, but remains above and apart from our bodies. Clothing is therefore metaphoric of that which transcends understanding and cannot be absorbed in the human mind.

That is why to fulfill this mitzvah the tzitzis fringes must be strung from a garment. For when the tzitzis extend from a garment they symbolize that all six hundred and thirteen mitzvos stem from G-d’s will that utterly transcends human understanding; likewise, our commitment to their observance must transcend reason. Without this recognition symbolized by the tallis, the tzitzis fringes alone do not represent the mitzvos at all.

—Likutei Sichos, vol. 2, pp. 324-325