律戒本疏 1.99

1.99

四十六到軍中乃至二夜應往過宿墮　雖有緣聽往。往應時返。六群比丘二宿不還。致人疑怪。因是復結。即聽二夜過是犯墮。

Forty-six: Arriving in an army, one may stay up to two nights; exceeding that and staying overnight is an offense of pāyattika. Although permitted to go if there is an occasion, having gone one should return at the proper time. The monks of the group of six stayed for two nights without returning, causing people to suspect and wonder. For this reason, it was again formulated: two nights are permitted; exceeding this commits an offense of pāyattika.