The Messenger of Allah ﷺ said during the Farewell Pilgrimage, "They are only four. Do not associate anything with Allah, do not kill a soul whom Allah has forbidden except by right, do not commit adultery, and do not steal."He said, "I have never been more careful to observe them than I have been since I heard them from the Messenger of Allah ﷺ."
قال رسول الله ﷺ في حجة الوداع: إنما هن أربع: لا تشركوا بالله شيئا، ولا تقتلوا النفس التي حرم الله إلا بالحق، ولا تزنوا، ولا تسرقوا. قال: فما أنا بأشح عليهن مني، إذ سمعتهن من رسول الله ﷺ.
Ahmad (1899), Nasai in Kubra (11309), and Hakim (4/351) all narrated it through the route of Mansur, from Hilal bin Yasaf, from Salama bin Qays Ashjai, who said, then he related it. Its chain of transmission is sahih.Regarding His saying, "except one who repents and believes and does righteous deeds", the scholars differed over whether a deliberate killer has repentance available to him or not. Ibn Abbas and others held that the deliberate killer has no repentance, while the majority of scholars held that the killer does have repentance. The detailed discussion of this has already been given in Surah Nisa at verse 93.As for His saying, "for those, Allah will change their evil deeds into good ones", this means their disbelief becomes faith, their worship of idols becomes obedience, and the evil deeds of their actions become good deeds, and this comes after repentance and turning back to Allah Most High, and their entering into Islam.