Musnad Abu Ya'la al-Mawsili 128:33

Bishr ibn al-Walid al-Kindi narrated to us, Abu Sahl Yusuf ibn Atiyyah al-Saffar narrated to us, he said: I heard Thabit saying: Anas said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The likeness of my Ummah is like the rain; it is not known whether its beginning is better or its end."