Siman - Berachos Daf 23

• Going to the bathroom before Shemoneh Esrei

One who feels the need to relieve himself and cannot restrain himself for 72 minutes (the time it takes to travel the distance of a parsah), should not begin Shemoneh Esrei. To do otherwise would be to render his tefillah a to’eivah (an abomination).

      -  The source for the need to prepare oneself for tefillah is the pasuk, הכון לקראת אלקיך

          ישראל – Prepare to meet your G-d, O Israel.

• Where to take tefillin off when going to the bathroom

One must remove his tefillin at least four amos way from an established bathroom before entering. If the place had never been used as a bathroom, he can take his tefillin off there and relieve himself, but he must move at least four amos away before putting them back on.

• Forbidden to store anything in a tefillin bag

It is forbidden to store anything other than tefillin in a bag set aside to hold tefillin.

- It’s a machlokes whether the bag becomes forbidden as soon as it is set aside for such usage

  (הזמנה   מילתא היא) or only after it has been used (הזמנה לאו מילתא היא).