Musannaf Ibn Abi Shayba 29:222

Shababa ibn Sawwar narrated to us, Sulayman ibn al-Mughira narrated to us, from Humayd ibn Hilal, from Abdullah ibn Mughaffal, who said: Abdullah ibn Salam passed by a land and said: "At the head of forty years, there will be peace at this place." He said: So the group of Mu'awiya was at the head of the forty years.