Musnad Ahmad 28:81

'Abd al-Rahman narrated to us, from Sufyan, from Abu Sinan, from 'Abd Allah ibn Abi al-Hudhayl, from 'Abd Allah ibn 'Amr, who said: "The Prophet, peace and blessings of Allah be upon him, used to seek refuge from knowledge that does not benefit, a supplication that is not heard, a heart that does not humble itself, and a soul that is not satisfied."