四分律刪補隨機羯磨 2.158

2.158

（時諸比丘一切時遊行，蹋殺生草木，斷眾生命根。世人譏呵，蟲鳥為譬。佛言：「不應一切時遊行，聽三月夏安居。」有通呵、別制，出在尼律。）

(At that time, the bhikṣus were traveling at all times, trampling to death living grasses and plants and severing the life-faculty of living beings. Worldly people criticized and scolded them, using insects and birds as parables. The Buddha said: 'You should not travel at all times; I permit a three-month summer varṣā.' General admonitions and specific prohibitions appear in the nuns' vinaya.)