Speak unto the children of Israel, and bid them that they make them fringes in the borders of their garments throughout their generations, and that they put upon the fringe of the borders a ribband of blue:
38 Speak unto the children of Israel. A little farther on I will explain the object of this precept more fully: although it is plain from the next verse that God had no other object but to exercise the Jews in constant meditation upon the Law.
Provision had been just now made by the law for the pardon of sins of ignorance and infirmity; now here is an expedient provided for the preventing of such sins. They are ordered to make fringes upon the borders of their garments, which were to be memorandums to them of their duty, that they might not sin through forgetfulness. 1.
Commenting on Numbers 15:37-41
And it shall be unto you for a fringe,.... The blue ribbon or lace shall be in or upon the fringe to fasten it: that ye may look upon it; the blue lace making the whole the more conspicuous: from hence the Jews gather, that the night is not the time for wearing fringe, which lessens the sight, and it is not so easily seen...