Verse 11.5.3.8

śauceyo jñaptaḥ prakṣyāmi tveva bhagavantamiti pṛcaiva prācīnayogyeti sa hovāca yasminkāla uddhṛtāste'gnayaḥ syurupāvahṛtāni pātrāṇi hoṣyantsyā atha ta āhavanīyo'nugacedvettha tadbhayaṃ yadatra juhvato bhavatīti vedeti hovāca purā cirādasya jyeṣṭhaḥ putro mriyeta yasyaitadaviditaṃ syādvidyābhistvevāhamatāriṣamiti kiṃ viditaṃ kā prāyaścittiriti prāṇa udānamapyagāditi gārhapatya āhutiṃ juhuyāṃ saiva prāyaścittirna tadāgaḥ kurvīyetyetannau bhagavantsaheti hovāca

Preview of English translation:

8. Shauceya, thus instructed, said, “I would yet ask thee a question, reverend sir.”—“Ask then, Pracinayogya!” he replied. He (Shauceya) said, “If, at the time when thy fires are taken out, and the sacrificial vessels brought down, thou wert going to offer, and the offering-fire were then to go out, dost thou know what danger there is in that case for him who offers?” 'I know,' he replied; 'before long the eldest son would die in the case of him who would not know this; but by dint of knowledge I myself have prevailed.'—“What is that knowledge, and what the atonement?” he asked.—“The breath of the mouth has entered the upward breathing—such (is the knowledge); and I should make the offering in the Garhapatya fire—that would be the atonement, and I should not be committing that sin.”—“This much, then, reverend sir, we two (know) in common,” said (Shauceya).

For a detailled translation, including proper diacritics and footnotes, go the full English translation.