Musnad Ahmad 32:772

Abu Kamil narrated to us, Hammad narrated to us, Thabit narrated to us, from Anas, that a man asked the Messenger of Allah, peace and blessings of Allah be upon him, about the Hour, and the prayer was called. When the Messenger of Allah, peace and blessings of Allah be upon him, finished his prayer, he said: "Where is the one who asked about the Hour?" The man said: Here I am, O Messenger of Allah. He said: "And what have you prepared for it, for it is surely coming?" He said: I have not prepared much work for it, except that I love Allah and His Messenger. He said: "Then you are with whom you love." He said: The Muslims did not rejoice at anything after Islam more than they rejoiced at this.