Muwatta Malik 1633
موطأ مالك#1633Da'ifوَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّ مُعَاذَ بْنَ جَبَلٍ، قَالَ آخِرُ مَا أَوْصَانِي بِهِ رَسُولُ اللَّهِ صلى الله عليه وسلم حِينَ وَضَعْتُ رِجْلِي فِي الْغَرْزِ أَنْ قَالَ " أَحْسِنْ خُلُقَكَ لِلنَّاسِ يَا مُعَاذُ بْنَ جَبَلٍ " .
Yahya related to me from Malik that Muadh ibn Jabal said, "The last advice the Messenger of Allah, may Allah bless him and grant him peace, gave me when I put my foot in the stirrup was that he said, 'Make your character good for the people, Muadh ibn Jabal
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 47:1