Musnad Ahmad 340:5

Abu al-Yaman narrated to us, he said: Isma'il ibn 'Ayyash narrated to us, from Muhammad ibn Ishaq, from Muhammad ibn 'Amr ibn 'Ata', from Nu'aym ibn Mujmir, from Rabi'ah ibn Ka'b, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said to me: "Ask me, and I shall give you." I said: "O Messenger of Allah, grant me respite so that I may consider my affair." He said: "Then consider your affair." He said: So I considered, and I said: "The affair of the world is fleeting, so I do not see anything better than something I take for myself for my Hereafter." Then I entered upon the Prophet, peace and blessings of Allah be upon him, and he said: "What is your need?" I said: "O Messenger of Allah, intercede for me with your Lord, the Almighty and Majestic, that He may free me from the Fire." He said: "Who commanded you to do this?" I said: "No, by Allah, O Messenger of Allah, no one commanded me to do it, but I considered my affair and saw that the world is departing from its people, so I loved to take for my Hereafter." He said: "Then assist me against your own self with an abundance of prostration."