Muwatta Malik 1635

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ عَلِيِّ بْنِ حُسَيْنِ بْنِ عَلِيِّ بْنِ أَبِي طَالِبٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مِنْ حُسْنِ إِسْلاَمِ الْمَرْءِ تَرْكُهُ مَا لاَ يَعْنِيهِ ‏"‏ ‏.‏

Yahya related to me from Malik from Ibn Shihab from Ali ibn Husayn ibn Ali ibn Abi Talib that the Messenger of Allah, may Allah bless him and grant him peace, said, "Part of the excellence of a man's Islam is that he leaves what does not concern him

Reference

Muwatta Malik 1635

In-book

Book 47, Hadith 3