Musnad Ahmad 28:228

Hashim narrated to us, Hajjaj informed us, 'Amr ibn Shu'ayb narrated to us, from his father, from his grandfather, that al-'As ibn Wa'il vowed during the Pre-Islamic period (Jahiliyyah) to slaughter one hundred camels. Hisham ibn al-'As slaughtered his share, which was fifty camels. 'Amr asked the Prophet, peace and blessings of Allah be upon him, about that. He said: "As for your father, had he affirmed the Oneness of Allah (Tawhid), and you had fasted and given charity on his behalf, that would have benefited him."