Manusmriti

siva.sh/manusmriti/8/109

असाक्षिकेषु त्वर्थेषु मिथो विवदमानयोः । अविन्दंस्तत्त्वतः सत्यं शपथेनापि लम्भयेत् ॥ १०९ ॥

sanskrit

If two (parties) dispute about matters for which no witnesses are available, and the (judge) is unable to really ascertain the truth, he may cause it to be discovered even by an oath.

english translation

asAkSikeSu tvartheSu mitho vivadamAnayoH | avindaMstattvataH satyaM zapathenApi lambhayet || 109 ||

hk transliteration by Sanscript