Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 8
Sanskrit:
एतदु हैव भगवतो विष्णो: सर्वदेवतामयं रूपमहरह: सन्ध्यायां प्रयतो वाग्यतो निरीक्षमाण उपतिष्ठेत नमो ज्योतिर्लोकाय कालायनायानिमिषां पतये महापुरुषायाभिधीमहीति ॥ ८ ॥
ITRANS:
etad u haiva bhagavato viṣṇoḥ sarva-devatāmayaṁ rūpam aharahaḥ sandhyāyāṁ prayato vāgyato nirīkṣamāṇa upatiṣṭheta namo jyotir-lokāya kālāyanāyānimiṣāṁ pataye mahā-puruṣāyābhidhīmahīti.
Translation:
My dear King, the body of the śiśumāra, as thus described, should be considered the external form of Lord Viṣṇu, the Supreme Personality of Godhead. Morning, noon and evening, one should silently observe the form of the Lord as the Śiśumāra-cakra and worship Him with this mantra: “O Lord who have assumed the form of time! O resting place of all the planets moving in different orbits! O master of all demigods, O Supreme Person, I offer my respectful obeisances unto You and meditate upon You.”