Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 44: Bhagīratha Delivers his Uncles
Text 1.44.4

सागरस्य जलं लोके यावत्स्थास्यति पार्थिव।
सगरस्यात्मजास्तावत्स्वर्गे स्थास्यन्ति देववत्॥

sāgarasya jalaṁ loke yāvat sthāsyati pārthiva
sagarasyātmajās
tāvat svarge sthāsyanti devavat

sāgarasya = of the ocean; jalam = the waters; loke yāvat = as long as; sthāsyati = exist on earth; pārthiva = O king; sagarasya = Sagara’s [caused by the sons of Sagara]; atmajāḥ = sons; tāvat svarge = in Svarga; sthāsyanti = will reside; devavat = like the devas.

O king, as long as the waters of the ocean [caused by the sons of Sagara] exist on earth, Sagara’s sons will reside in Svarga like the devas.

This is the specialty of their attainment of Svarga.