Musnad Ahmad 5:260

Sa'id ibn Mansur narrated to us, Isma'il ibn Zakariyya narrated to us, from Hajjaj ibn Dinar, from al-Hakam, from Hujayyah ibn 'Adi, from 'Ali: That al-'Abbas ibn 'Abd al-Muttalib asked the Prophet, peace and blessings of Allah be upon him, about hastening his charity before it became due, and he granted him a concession for that.