四分比丘戒本疏 2.73

2.73

The forty-third precept: Regarding 'in a household of food where there are jewels'—a man and woman, depending on each other, mutually give rise to greed and pleasure, which in sense is identical to food. If the conditions of greed are not severed, the object they love is in sense identical to jewels. This refers to when a husband and wife are mutually affectionate and defiled, and a monk forcefully sits there, impeding their sexual acts; thus he commits an offence. If there is a wise man who serves as a fourth person, he commits no offence. The Vinaya Master of Nanshan says that this is touching food. That is truly laughable.