Sayyidah Habibah bint Abi Tajra'ah (may Allah be pleased with her) said: I found myself with some women of Quraysh in the house of Abu Husayn, while the Messenger of Allah (peace and blessings be upon him) was between Safa and Marwah. She said: When he (peace and blessings be upon him) reached the place of running (al-mas'a), I heard him say: "Perform the sa'i, for Allah has made the sa'i obligatory upon you."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20942