Shat.Upa 01.09

māso vai prajāpatiḥ। tasya kṛṣṇapakṣa eva rayiḥ। śuklaḥ prāṇastasmādete ṛṣayaḥ śukla iṣṭiṃ kurvantītara itarasmin। ahorātre vai prajāpatiḥ। tasyāhareva prāṇo rātrireva rayiḥ। prāṇaṃ vā ete praskandanti ye divā ratyā saṃyujyante। brahmacaryameva tadyadrātrau ratyā saṃyujyante ॥9॥

The month is considered to be the lord Prajāpati. Its dark fortnight represents 'rayi', i.e. wealth. The bright fortnight symbolizes 'Prāṇa', i.e. life, and therefore, sages perform bright sacrifices during this time. Day and night are also seen as the lord Prajāpati, with day representing life and night representing wealth. Those who engage in activities during the day are said to leap towards life, while celibacy is associated with those who leap forward at night.

Bhāṣya 01.09

In the couple, divine Vishnu resides in the wife as Saraswati, and in the husband as Vayu. By understanding this, one attains liberation.

"māsasthitaḥ sa bhagavān pakṣayorvākca mārutaḥ। ahorātre tu bhagavān prāṇo hyahani vāṅniśi॥

"The Lord is situated in the month, representing speech and wind during the fortnights, respectively. The day and night are that Lord, embodying life air during the day and speech at night.

dampatyorbhagavān viṣṇuḥ bhāryāsthā tu sarasvatī। bhartṛsthaḥ sa svayaṃ vāyuḥ evaṃ jānan vimucyate॥"

In the couple, divine Vishnu resides in the wife as Saraswati, and in the husband as Vayu. Understanding this, one attains liberation."

iti prajāpati-saṁhitāyām।

- stated thus in the collection of Prajapati Vedic hymns.