Manusmriti
छायायामन्धकारे वा रात्रावहनि वा द्विजः । यथासुखमुखः कुर्यात् प्राणबाधभयेषु च ॥ ५१ ॥
In the shade or in darkness a Brahmana may, both by day and at night, do it, assuming any position he pleases; likewise when his life is in danger.
english translation
chAyAyAmandhakAre vA rAtrAvahani vA dvijaH । yathAsukhamukhaH kuryAt prANabAdhabhayeSu ca ॥ 51 ॥
hk transliteration by Sanscript