לֹעֵ֣ג לָ֭רָשׁ חֵרֵ֣ף עֹשֵׂ֑הוּ שָׂמֵ֥חַ לְ֝אֵ֗יד לֹ֣א יִנָּקֶֽה׃
Shulchan Arukh, Orach Chayim
The laws of tefillin in a cemetery and in a bathhouse: containing two subsections. It is forbidden to enter a cemetery, or within four cubits of a corpse, with tefillin on one's head, because of mocking the poor (lo'eg larash). And if they [the tefillin] are covered, this is permitted.