Musnad Ahmad 1153:1614

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Hisham, from his father, from 'Aisha, who said: The Messenger of Allah (peace and blessings of Allah be upon him) entered upon me while there was a woman with me who was of good appearance. He said: "Who is this?" I said: "This is so-and-so, daughter of so-and-so, O Messenger of Allah; she does not sleep at night." He said: "Desist, desist. Take from the deeds what you can bear, for Allah the Almighty and Majestic does not grow weary until you grow weary. And the most beloved of deeds to Allah the Almighty and Majestic is that which its doer persists in, even if it is little."