佛說目連問戒律中五百輕重事經 2.105

2.105

問：「比丘舍內都不著三衣，犯何事？」答：「坐禪誦經不著，犯墮。」

Question: "If a bhikṣu does not wear any of the three robes inside his room, what offense does he commit?" Answer: "If he sits in meditation or recites scriptures without wearing them, he commits a pāyattika."