Gobhilagrihyasutra 2.6.3

2.6.3

paścāt patir avasthāya, dakṣiṇena pāṇinā dakṣiṇam am̐sam anvavamṛśyā 'nantarhitaṃ nābhideśam abhimṛśet pumām̐sau mitrāvaruṇāv ity etaya rcā.

Her husband, standing behind her, should grasp down with his right hand over her right shoulder, and should touch the uncovered place of her navel with the verse, 'The two men, Mitra and Varuna' (MB. I, 4, 8).