مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4236
Musnad of Abdullah bin Mas'ood
It was narrated that ‘Abdullah said: The Messenger of Allah (ﷺ) said: "Repentance from sin means repenting from it and not going back to it.”
Musnad Ahmad 4264Its isnad is da'eef]