四分律刪繁補闕行事鈔 1.162

1.162

上明僧相，並形同出家，相有濫故，得共法事。必著俗服，相形明了，亦無同法之義。《十誦》白衣，謂本受戒不得者。亦有受後難緣，須著俗服者，亦應同法，由本是僧。即知作法之時，窮問界內俗人之中，頗有曾受具戒不捨者不？要答無者，方無別眾。

Above, the characteristics of the saṃgha have been explained: they all appear identical to the renunciant state, and because their appearance may be confused, they can participate in formal acts. If one definitely wears secular clothing, the appearance is distinct, and there is no basis for participating in the procedure. The 'layperson' in the Daśādhyāya-vinaya refers to one who originally failed to obtain the precepts. There are also those who, having received them, encounter difficult circumstances and must wear secular clothing; these should also participate in the procedure, because they are fundamentally monks. Thus we know that when performing the procedure, one must thoroughly question whether among the secular people within the boundary there are any who once received the full precepts and have not relinquished them. Only when they answer that there are none is there no separate saṃgha.