PRAŚNA UPANISHAD · 1.13

अहोरात्रो वै प्रजापतिस्तस्याहरेव प्राणो रात्रिरेव रयिः प्राणं वा एते
प्रस्कन्दन्ति ये दिवा रत्या संयुज्यन्ते ब्रह्मचर्यमेव तद्यद्रात्रौ
रत्या संयुज्यन्ते ॥ १.१३॥

ahorātro vai prajāpatistasyāhareva prāṇo rātrireva rayiḥ prāṇaṃ vā ete
praskandanti ye divā ratyā saṃyujyante brahmacaryameva tadyadrātrau
ratyā saṃyujyante ॥ 1.13॥

“Day and night also are the Eternal Father, whereof the day is Life and the night is Matter. Therefore do they offend against their own life who take joy with woman by day; by night who take joy, enact holiness.

Sri Aurobindo · CWSA 18, p. 178