PRAŚNA UPANISHAD · 1.12

मासो वै प्रजापतिस्तस्य कृष्णपक्ष एव रयिः शुक्लः प्राणस्तस्मादेत
ऋषयः शुक्ल इष्टं कुर्वन्तीतर इतरस्मिन् ॥ १.१२॥

māso vai prajāpatistasya kṛṣṇapakṣa eva rayiḥ śuklaḥ prāṇastasmādeta
ṛṣayaḥ śukla iṣṭaṃ kurvantītara itarasmin ॥ 1.12॥

“The month also is that Eternal Father, whereof the dark fortnight is Matter the Female and the bright fortnight is Life the Male. Therefore do one manner of sages offer sacrifice in the bright fortnight and another in the dark.