Musnad Ahmad 30:1292

Abu al-Nadr narrated to us, Abd al-Rahman narrated to us, from his father, from Abu Salih, from Abu Hurairah, from the Prophet, may God bless him and grant him peace, who said: "Indeed, the servant speaks a word from the pleasure of God, not giving it any thought, by which God raises him in degrees. And indeed, the servant speaks a word from the wrath of God, not giving it any thought, by which he falls into Hell."