(Exodus 13:10) "And you shall keep this statute in its time": What is the intent of this? From "And it shall be to you as a sign upon your hand," I might think that (the mitzvah of tefillin (leather phylacteries worn during prayer)) obtains with minors, too. And it also follows, viz.: Since Torah (study) and tefillin are both positive commandments, then if we have learned about Torah (study) that it obtains with minors as well as with adults, the same is true of tefillin. It is, therefore, written "And you shall keep this statute"—(The mitzvah of tefillin obtains) only with one who can keep his tefillin (in a state of cleanliness). From here they ruled: If a minor is capable of keeping his tefillin (in a state of cleanliness), his father makes him tefillin.