Musnad Ahmad 30:1818

Qutaybah ibn Sa'id narrated to us, he said: Ibn Lahi'ah narrated to us, from Yazid ibn Abi Habib, from 'Isa ibn Talhah, from Abu Hurairah, that Khawlah bint Yasar came to the Prophet, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, I have only one garment, and I menstruate in it, so what should I do?" He said: "When you become pure, wash it, then pray in it." She said: "What if the blood does not come out?" He said: "The water is sufficient for you, and its trace will not harm you."