Musnad Ahmad 1246:2

Abu Nu'aym narrated to us, he said: Al-Walid narrated to us, he said: My grandmother narrated to me, from Umm Waraqah bint 'Abdullah ibn al-Harith al-Ansariyyah, and she had collected the Quran. "And the Prophet, peace and blessings of Allah be upon him, had commanded her to lead the people of her household in prayer." And she had a caller to prayer (mu'adhdhin), and she used to lead the people of her household in prayer.