Musnad Ahmad 1153:2020

Mu'adh narrated to us, he said: Muhammad ibn 'Amr informed us, from Abu Salamah, from 'Aishah, she said: We had a mat that we would spread out during the day, and we would partition it off at night. The Messenger of Allah (peace and blessings of Allah be upon him) prayed on it one night, and the Muslims heard his recitation, so they prayed with his prayer. When the second night came, they increased in number, so he looked out toward them and said: "Take upon yourselves of deeds that which you can bear, for Allah does not grow weary until you grow weary." And the most beloved of deeds to him was that which was most constant, even if it were little. She said: "And when he performed a prayer, he would make it firm."