Most probably the reference is to different materials, interwoven in the yarn of which the dress was made; but a difficulty still remains in the fact that such admixture was ordered in the garments of the priests. Perhaps the best explanation is that of Josephus, that the law here was only intended for the laity; which, as no question of intrinsic morality was involved, might easily have been. But when we inquire as to the reason of these prohibitions, and especially of this last one, it must be confessed that it is hard for us now to speak with confidence. Most probable it appears that they were intended for an educational purpose, to cultivate in the mind of the people the sentiment of reverence for the order established in nature by God. For what the world calls the order of nature is really an order appointed by God, as the infinitely wise and perfect One; hence, as nature is thus a manifestation of God, the Hebrew was forbidden to seek to bring about that which is not according to nature, unnatural commixtures; and from this point of view, the last of the three precepts appears to be a symbolic reminder of the same duty, namely, reverence for the order of nature, as being an order determined by God. (S. H. Kellogg, D. D.)
Woollen and flaxen threads
Not only is it forbidden to weave woollen and flaxen threads together into one material to make wearing apparel of it; but, according to the administrators of the law during the second Temple, an Israelite must not mend a woollen garment with a flaxen thread, and vice versa. One of the reasons which the ancient canonists assign for this prohibition is that “wool and linen were appointed for the priests alone.” This law is observed by the orthodox Jews to this day. (C. D. Ginsburg, LL. D.)
