Musnad Ahmad 482:65

Musa ibn Dawud narrated to us, he said: Ibn Lahi'ah narrated to us, from Yazid ibn Abi Habib, from Abu al-Khayr, from Uqbah ibn Amir, who said: A man came to the Prophet, peace and blessings of Allah be upon him, and said: "My mother has died, and I wish to give charity on her behalf." He said: "Did she command you?" He said: "No." He said: "Then do not do it."