Musnad Ahmad 1153:2077

Uthman ibn Umar narrated to us, he said: Yunus narrated to us, from al-Zuhri, from Urwah, from Aisha, that al-Hawla bint Tuwayt passed by Aisha while the Messenger of Allah, peace and blessings of Allah be upon him, was with her. She said: So I said, "O Messenger of Allah, this is al-Hawla, and they claim that she does not sleep at night." He said: "She does not sleep at night? Take upon yourselves of the deeds what you can bear, for by Allah, Allah does not grow weary until you grow weary."