Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 3
दर्शयामास तं देवी प्रसन्ना वरदास्मि ते ।इत्युक्त: स्वमभिप्रायं शशंसावनतो नृप: ॥ ३ ॥
darśayām āsa taṁ devīprasannā varadāsmi teity uktaḥ svam abhiprāyaṁśaśaṁsāvanato nṛpaḥ
Thereafter, mother Ganges appeared before King Bhagīratha and said, “I am very much satisfied with your austerities and am now prepared to give you benedictions as you desire.” Being thus addressed by Gaṅgādevī, mother Ganges, the King bowed his head before her and explained his desire.
The King’s desire was to deliver his forefathers, who had been burnt to ashes because of disrespecting Kapila Muni.