Musnad Ahmad 26:857

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Sulayman, who said: I heard Abu Wa'il narrating from Abdullah, who said: We said: "O Messenger of Allah, do you see what we did during the time of polytheism—will we be held accountable for it?" He said: "Whoever among you does good in Islam will not be held accountable for what he did during the time of polytheism. And whoever among you does evil in Islam will be held accountable for what he did during the time of polytheism and Islam."