Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 18
Sanskrit:
यस्माद्बिभेम्यहमपि द्विपरार्धधिष्ण्य-मध्यासित: सकललोकनमस्कृतं यत् ।तेपे तपो बहुसवोऽवरुरुत्समान-स्तस्मै नमो भगवतेऽधिमखाय तुभ्यम् ॥ १८ ॥
ITRANS:
yasmād bibhemy aham api dviparārdha-dhiṣṇyamadhyāsitaḥ sakala-loka-namaskṛtaṁ yattepe tapo bahu-savo ’varurutsamānastasmai namo bhagavate ’dhimakhāya tubhyam
Translation:
Your Lordship, I offer my respectful obeisances unto You who are indefatigable time and the enjoyer of all sacrifices. Although I am situated in an abode which will continue to exist for a time duration of two parārdhas, although I am the leader of all other planets in the universe, and although I have undergone many, many years of penance for self-realization, still I offer my respects unto You.
Purport:
Brahmā is the greatest personality in the universe because he has the longest duration of life. He is the most respectable personality because of his penance, influence, prestige, etc., and still he has to offer his respectful obeisances unto the Lord. Therefore, it is incumbent upon all others, who are far, far below the standard of Brahmā, to do as he did and offer respects as a matter of duty.