Matsyapurana 121.38

121.38

nadīṃ bhagīrathasyārthe tapasogreṇa toṣitaḥ
tato visarjayāmāsa sapta srotāṃsi gaṅgayā //

Being pleased with the devotion of Bhagîratha, the Lord, for his sake, let the river loose into seven branches, three of which went to the East, three to the West (and one near Himself), thus the three-wayed Ganges become flowed in seven streams.—38-39.