Bulugh al-Maram, Book 16, Hadith 1477 (In-Book)

Anas (RAA) narrated that Allah's Messenger said: “All the sons of Adam are sinners, but the best of sinners are those who repent often.” Related by At·Tirmidhi and Ibn Majah with a strong chain of narrators.

وَعَنْ أَنَسٍ ‏- رضى الله عنه ‏- قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ كُلُّ بَنِي آدَمَ خَطَّاءٌ, وَخَيْرُ اَلْخَطَّائِينَ اَلتَّوَّابُونَ } أَخْرَجَهُ اَلتِّرْمِذِيُّ, وَابْنُ مَاجَهْ, وَسَنَدُهُ قَوِيٌّ.‏ (1936)‏.‏ ‏1 ‏- حسن.‏ رواه الترمذي (2499)‏، وابن ماجه (2451)‏.‏

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also referenced under: Book 16, Hadith 1520 (English)