Why is the mitzvah of tefellin not by night?

Question

Berachos discusses the importance of saying shema while wearing tefellin. Saying shema without tefellin is likened to bringing an incomplete sacrifice (Berachos, 14b). Similiary, one who washes his hands, wraps tefellin, says shema, and prays, is likened to building an alter and putting a sacrifice upon it (Berachos, 15b). Since we have the obligation to say shema twice a day (Berachos, 2a), why is it that we do not wrap tefellin in the evening? Where is this discussed?

(Side question: where does one go to get the text to paste in here for quoting text in the Talmud?)

Answer 1

Shulchan Oruch Orach Chayyim 30 (2) MB [3, 4] forbids wearing Tefillin at nighttime. MB explains that this is a Rabbinic prohibition in case he would fall asleep wearing them and emit wind from below.

The source seems to be the gemoro in Shabbos 49a about half-way down. The link here will show you where to access the gemoro text to paste in.

א"ר ינאי תפילין צריכין גוף נקי כאלישע בעל כנפים מאי היא אביי אמר שלא יפיח בהן רבא אמר שלא יישן בהן