Musnad Ahmad 562:2

Sufyan ibn 'Uyaynah narrated to us, he said: 'Amr—meaning Ibn Dinar—said: I said to Abu al-Sha'tha': "They claim that the Messenger of Allah (peace and blessings of Allah be upon him) forbade the meat of donkeys." He said: "O 'Amr, the 'Sea' refused that," and he recited: {Say, "I do not find within that which was revealed to me [anything] forbidden to one who would eat it..."} [Al-An'am: 145]. "O 'Amr, the 'Sea' refused that. Al-Hakam ibn 'Amr al-Ghifari used to say that." He means by his saying "the 'Sea' refused that for us": Ibn 'Abbas.