Musnad Abu Ya'la al-Mawsili 148:3

Abu Bakr ibn Abi Shaybah narrated to us, Shababah narrated to us, from Layth, from Yazid ibn Abi Habib, from Sa'id ibn Sinan, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The greatness of the reward is with the greatness of the trial."