Musnad Ahmad 1153:1927

Ibn Numayr narrated to us, from Hisham, from his father, from Aisha, who said: A woman from Banu Asad was with her, and the Prophet, may Allah bless him and grant him peace, entered and said: "Who is this?" She said: "This is so-and-so, she does not sleep [due to prayer]." The Prophet, may Allah bless him and grant him peace, said: "Take upon yourselves what you can bear, for by Allah, Allah the Almighty does not grow weary until you grow weary. The most beloved of religion to Allah the Almighty is that which its practitioner persists in."