Musnad Ahmad 1153:493

Hassan narrated to us, Shayban narrated to us, from Yahya, from Muhammad ibn Ibrahim, from Yuhannis, that Aisha informed him that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If the people knew what is in the night prayer (al-'atamah) and the morning prayer, they would come to them even if they had to crawl."