With their water gone and her baby crying for thirst, Hajrah رضي الله عنها ran in search of help — climbing the hill of Safa to look out, then hurrying to Marwah, back and forth seven times. She did not despair of Allah's mercy.
Then, by the feet of the infant Isma'il عليه السلام, water burst forth from the ground — the well of Zamzam. Hajrah رضي الله عنها began to contain the gushing water, saying “zam, zam” (“stop, stop”), and from this the well takes its name.
Indeed, the hills of Safa and Marwah are among the symbols of Allah.
The etiquette of drinking Zamzam
It is recommended to face the qibla, say Bismillah, drink in three breaths, and make sincere du'a — for Zamzam, the Prophet ﷺ taught, is for whatever it is drunk for.
This account is compiled from trusted sources and the classical tafsir (including Ibn Kathir); see Qur'an 2:158.