四分律行事鈔資持記 3.103

3.103

In [item] three, the Daśādhyāya-vinaya says: It must not be single-layered; originally intended to cushion the body, it is prohibited that it must be thick and heavy. Passing the night separated from it incurs a duṣkṛta; being an article that constantly follows one, separation from it is rare and not grave. The Saṃghāvaśeṣa Commentary says: "Not prohibited by the Buddha" means that among the niḥsargika-pāyattika rules there is no such precept. It is not appropriate to consider it only a duṣkṛta, nor does one lose the formal reception.