四分律比丘含注戒本 2.291

2.291

若不捨前請，受後請，咽咽墮。若不捨後請，受前請，咽咽吉羅。不犯者：病時；施衣時；若一日之中有多請，自受一請，餘者當施與人，言「長老，我應往彼，今布施汝」。若與非食，或不足，或無請食者，或食已更得食，或一處有前食、後食，皆開。

(If one does not relinquish the prior invitation and accepts a subsequent invitation, with each swallow a falling [offence] is incurred. If one does not relinquish the subsequent invitation and accepts the prior invitation, with each swallow a duṣkṛta is incurred. As for non-offences: a time of illness; a time of robe-giving; if within a single day there are multiple invitations and one accepts one invitation oneself, one should give the others to someone else, saying, 'Venerable, I should have gone there, but now I give it to you'; or if one is given non-food; or if it is insufficient; or if there is no one who invited him for food; or if having eaten one gets further food; or if in one place there is prior food and subsequent food—all these are permitted.)