SB 4.8.20

yasyāṅghri-padmaṁ paricarya viśva-
 vibhāvanāyātta-guṇābhipatteḥ
ajo ’dhyatiṣṭhat khalu pārameṣṭhyaṁ
 padaṁ jitātma-śvasanābhivandyam
Synonyms: 
yasya — whose; aṅghri — leg; padmam — lotus feet; paricarya — worshiping; viśva — universe; vibhāvanāya — for creating; ātta — received; guṇa-abhipatteḥ — for acquiring the required qualifications; ajaḥ — the unborn (Lord Brahmā); adhyatiṣṭhat — became situated; khalu — undoubtedly; pārameṣṭhyam — the supreme position within the universe; padam — position; jita-ātma — one who has conquered his mind; śvasana — by controlling the life air; abhivandyam — worshipable.
Translation: 
Sunīti continued: The Supreme Personality of Godhead is so great that simply by worshiping His lotus feet, your great-grandfather, Lord Brahmā, acquired the necessary qualifications to create this universe. Although he is unborn and is the chief of all living creatures, he is situated in that exalted post because of the mercy of the Supreme Personality of Godhead, whom even great yogīs worship by controlling the mind and regulating the life air [prāṇa].
Purport: 

Sunīti cited the example of Lord Brahmā, who was Dhruva Mahārāja’s great-grandfather. Although Lord Brahmā is also a living being, by his penance and austerity he acquired the exalted position of creator of this universe by the mercy of the Supreme Lord. To become successful in any attempt, one not only has to undergo severe penances and austerities, but also must be dependent on the mercy of the Supreme Personality of Godhead. This indication had been given to Dhruva Mahārāja by his stepmother and was now confirmed by his own mother, Sunīti.