Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.20

2.5.2.20

atha pratiprasthātā pratiparaiti | sa patnīmudāneṣyanpṛcati kena carasīti varuṇyaṃ vā etatstrī karoti yadanyasya satyanyena caratyatho nenme 'ntaḥśalpā juhavaditi tasmātpṛcati niruktaṃ vā enaḥ kanīyo bhavati satyaṃ hi bhavati tasmādveva pṛcati sā yanna pratijānīta jñātibhyo hāsyai tadahitaṃ syāt

Thereupon the Pratiprasthâtri returns (to where the sacrificer's wife is seated). When he is about to lead the wife away, he asks her, 'With whom holdest thou intercourse?' Now when a woman who belongs to one (man) carries on intercourse with another, she undoubtedly commits (a sin) against Varuna. He therefore thus asks her, lest she should sacrifice with a secret pang in her mind; for when confessed the sin becomes less, since it becomes truth; this is why he thus asks her. And whatever (connection) she confesses not, that indeed will turn out injurious to her relatives.