Shiva Purana
अद्यैव सप्तमी या सा गंगारूपास्ति तत्र वै॥ इत्युक्त्वान्तर्दधे देवी सा गंगा मुनिसत्तमाः ॥ ६१ ॥
Today is that seventh day. The river is in the form of Gaṅgā there.” Saying so the lady vanished. O excellent sages, she was Gaṅgā herself.
english translation
adyaiva saptamI yA sA gaMgArUpAsti tatra vai॥ ityuktvAntardadhe devI sA gaMgA munisattamAH ॥ 61 ॥
hk transliteration by Sanscript