´It was narrated that 'Ali, may Allah be pleased with him, said:` "The Messenger of Allah said: 'I have exempted you from (having to pay Zakah on) houses and slaves, and there is no Zakah on less than two hundred (Dirhams)."
Hadith ReferenceSunan an-Nasa'i / The Book of Zakah / Hadith: 2480
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:ضعيف، إسناده ضعيف، ابو داود (1574) ترمذي (620) ابن ماجه (1790) انوار الصحيفه، صفحه نمبر 340