Salih bin Kaysan narrated that Abdullah bin Abi Umamah bin Tha'labah narrated from his father, Sayyiduna Abu Umamah (may Allah be pleased with him), that he used to say: the Messenger of Allah (peace and blessings be upon him) said: "Indeed, simplicity is part of faith. Indeed, simplicity is part of faith."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 786