四分律比丘含注戒本 3.209

3.209

不犯者：或時有病；比座眼闇，如前方便；或看日時；或命、梵二難欲逃避，左右看視者。

Those who do not commit an offense: at times one is ill; the neighboring seat has dim eyes, using skillful means as before; or checking the time of day; or wishing to escape the two perils of life and celibacy, looking left and right.