API
An-Nawawy’s Forty Hadiths: (12) Being Concerned with Beneficial Matters
On the authority of Abu Hurayrah (may Allah be pleased with him) who said, "The Messenger of Allah (peace and blessings of Allah be upon him) said, 'Part of the perfection of one’s Islam is his leaving that which does not concern him.'" A hasan (good) hadeeth which was related by at-Tirmidhi and others in this fashion.
