277. Things That Preclude Davening

Tefillah u’Birkas Kohanim 3:11

If one has two prayers to be recited, mincha and musaf, he should daven mincha first and then musaf. Some say that this should not be done in shul, so that others should not make a mistake.

Tefillah u’Birkas Kohanim 4:1         

Five things keep a person from davening, even though the proper time has arrived: (1) the cleanliness of his hands; (2) covering his nudity; (3) the cleanliness of the place where he is to daven; (4) things that might agitate and distract him; (5) having proper intentions in his heart.