Simply by having water from the Ganges come in contact with the ashes of their burnt bodies, the sons of Sagara Mahārāja were elevated to the heavenly planets. Therefore, what is to be said of a devotee who worships mother Ganges faithfully with a determined vow? One can only imagine the benefit that accrues to such a devotee.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
भस्मीभूताङ्गसङ्गेन स्वर्याताः सगरात्मजाः । किं पुनः श्रद्धया देवीं ये सेवन्ते धृतव्रताः
bhasmībhūtāṅgasaṅgena svaryātāḥ sagarātmajāḥ | kiṃ punaḥ śraddhayā devīṃ ye sevante dhṛtavratāḥ
SB 9.9.13