Musnad Ahmad 25:447

'Affan narrated to us, Hammad narrated to us, 'Ata' ibn al-Sa'ib informed us, from Sa'id ibn Jubayr, from Ibn 'Abbas: That Ibrahim brought Isma'il—peace be upon them both—and Hajar, and placed them in Makkah at the location of Zamzam. He mentioned the hadith. Then she came from al-Marwah to Isma'il, and the spring had gushed forth. She began to scoop the water with her hand like this, until the water gathered in its hollow, then she would take it with her vessel and put it into her waterskin. The Messenger of Allah (peace be upon him) said: "May Allah have mercy on her; had she left it, it would have been a flowing spring running until the Day of Resurrection."