{To be seen of men} (pros to theath(886e)ai tois anthr(9370)ois).
See  6:1  where this same idiom occurs. Ostentation regulates the
conduct of the rabbis. {Phylacteries} (phulakt(8872)ia). An
adjective from phulakt(8872), phulass(935c) (to guard). So a fortified
place, station for garrison, then a safeguard, protecting charm
or amulet. The rabbis wore 	ephillin or prayer-fillets, small
leather cases with four strips of parchment on which were written
the words of  Ex 13:1-10,11-16  De 6:4-9  11:13-21 . They took
literally the words about "a sign unto thy hand," "a memorial
between thine eyes," and "frontlets." "That for the head was to
consist of a box with four compartments, each containing a slip
of parchment inscribed with one of the four passages. Each of
these strips was to be tied up with a well-washed hair from a
calf's tail; lest, if tied with wool or thread, any fungoid
growth should ever pollute them. The phylactery of the arm was to
contain a single slip, with the same four passages written in
four columns of seven lines each. The black leather straps by
which they were fastened were wound seven times round the arm and
three times round the hand. They were reverenced by the rabbis as
highly as the scriptures, and, like them, might be rescued from
the flames on a sabbath. They profanely imagined that God wore
the _tephillin_" (Vincent). It is small wonder that Jesus
ridiculed such minute concern for pretentious externalism and
literalism. These _tephillin_ "are still worn at the present day
on the forehead and left arm by Jews at the daily Morning Prayer"
(McNeile) . "The size of the phylacteries indexed the measure of
zeal, and the wearing of large ones was apt to take the place of
obedience" (Bruce). Hence they made them "broad." The
superstitious would wear them as mere charms to ward off evil.
{Enlarge the borders} (megalunousin ta kraspeda). In  9:20  we
see that Jesus, like the Jews generally, wore a tassel or tuft,
hem or border, a fringe on the outer garment according to  Nu
15:38 . Here again the Jewish rabbi had minute rules about the
number of the fringes and the knots (see on 消:20|). They made a
virtue of the size of the fringes also. "Such things were useful
as reminders; they were fatal when they were regarded as charms"
(Plummer).