The Rabbis have taught that a man should not drink water on Wednesdays
and Saturdays after night-fall, for if he does, his blood, because of
risk, will be upon his own head. What risk? That from an evil spirit who
on these evenings prowls abroad. But if the man be thirsty, what is he
to do? Let him repeat over the water the seven voices ascribed to the
Lord by David in Psalm xxix. 3-9, "The voice of the Lord is upon the
THE TALMUD, _P'sachim_, fol. 112, col. 1.