Ancient tefillin on graph paper, all from Qumran. Those on left are head tefillin, the one on the right an arm tefillin. Unlike modern tefillin, which are square, the ancient ones were rectangular. Note the various widths. (the bottom one is only 3/4 preserved and would have been the widest). The widest ones illustrate Jesus' reference to showy people making their phylacteries "broad" to flaunt their piety (Matthew 23: 5). Before we discovered that ancient tefillin were rectangular, we didn't know what he meant by "making broad."