俱舍論疏 13.164

13.164

論「於中不善至無慚無愧故」，釋不善者唯在欲界。自性不善，謂三不善及無慚愧，思等與此相應故成不善，身、語表業由此等起故成不善。上界既無自性不善，由此亦無諸不善業。

The commentary states: "Among them, the unwholesome ... because of the absence of shamelessness and non-dread." This explains that the unwholesome exists only in the desire realm. What is unwholesome by intrinsic nature refers to the three unwholesome [roots] as well as absence of shame and non-dread; volition and other factors are associated with these and therefore become unwholesome, and bodily and vocal vijñapti-karma are originated by these and therefore become unwholesome. Since the higher realms lack what is unwholesome by intrinsic nature, on this account they also lack all unwholesome karma.