PrU 1.13
अहोरात्रो वै प्रजापतिः । तस्याहरेव प्राणो रात्रिरेव रयिः । प्राणं वा एते प्रस्कन्दन्ति ये दिवा रत्या संयुज्यन्ते । ब्रह्मचर्यमेव तद्यद्रात्रौ रत्या संयुज्यन्ते
ahorātro vai prajāpatiḥ | tasyāhareva prāṇo rātrireva rayiḥ | prāṇaṃ vā ete praskandanti ye divā ratyā saṃyujyante | brahmacaryameva tadyadrātrau ratyā saṃyujyante
Devanagari rendered by HREEM from the edition's roman (IAST) text; the IAST is the edition's own.
Day and Night are Pragâpati; its day is spirit, its night matter. Those who unite in love by day waste their spirit, but to unite in love by night is right.
Translated by F. Max Müller