مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3863
Musnad of Abdullah bin Mas'ood
It was narrated that Ibn Mas'ood (رضي الله عنه) said: A man said to the Prophet (ﷺ): Will one of us be blamed for what he did during the Jahiliyyah? He said: "whoever does well in Islam will not be blamed for what he did during the Jahiliyyah, but whoever does badly in Islam will be blamed for his earlier and later actions."
Musnad Ahmad 3886Its isnad is saheeh, al-Bukhari (6921) and Muslim (120)]