Phylacteries. Said to be based on Greek charms/amulets. Rabbinical Judaism claims it is a literal interpretation of Exodus 13:9, Deut 6:6-8, and Deut 11:18. Originally started out approximately 1cm cubed. Jesus warned of the Pharisees’ practice of making their phylacteries broad (modern tefillin are approximately 5cm cubed with broader corresponding straps) – (Matt 23:5).