Apastambadharmasutra 2.3.7.15

2.3.7.15

yasya-[uddhṛteṣv [ahuteṣv agniṣv atithir [abhyāgacchet svayam enam [abhyudetya [brūyāt vrātya [atisṛja [hoṣyāmi / ity [atisṛṣṭena [hotavyam / [anatisṛṣṭaś cej-[juhuyād doṣaṃ brāhmaṇam [āha //

If a guest comes, after the fires have been placed (on the altar), but before the oblations have been offered, (the host) himself shall approach him and say to him: 'O faithful fulfiller of thy vows give me permission; I wish to sacrifice.' Then he shall sacrifice, after having received permission. A Brâhmana declares that he commits a sin if he sacrifices without permission.