Musnad Ahmad 31:59

Abu Sa'id narrated to us, Abd al-Rahman ibn Abi al-Rijal narrated to us, 'Umarah ibn Ghaziyyah narrated to us, from Abd al-Rahman ibn Abi Sa'id, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever asks while he possesses the value of an *uqiyyah* has importuned."