Musnad Ahmad 1015:7

Abu al-Mughirah narrated to us, Safwan narrated to us, from Shurayh ibn Ubayd al-Hadrami, that when death approached Abu Malik al-Ash'ari, he said: "O listener of the Ash'ariyyin, let the one who is present among you inform the one who is absent: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: 'The sweetness of the world is the bitterness of the Hereafter, and the bitterness of the world is the sweetness of the Hereafter.'"