Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 13


तपसाराध्य पुरुषं तस्यैवानुग्रहेण मे ।गर्भे त्वं साधयात्मानं यदीच्छसि नृपासनम् ॥ १३ ॥


tapasārādhya puruṣaṁtasyaivānugraheṇa megarbhe tvaṁ sādhayātmānaṁyadīcchasi nṛpāsanam


If you at all desire to rise to the throne of the King, then you have to undergo severe austerities. First of all you must satisfy the Supreme Personality of Godhead, Nārāyaṇa, and then, when you are favored by Him because of such worship, you shall have to take your next birth from my womb.


Suruci was so envious of Dhruva Mahārāja that she indirectly asked him to change his body. According to her, first of all he had to die, then take his next body in her womb, and only then would it be possible for Dhruva Mahārāja to ascend the throne of his father.