Musnad Abu Ya'la al-Mawsili 42:72

Ahmad ibn Isa narrated to us, Ibn Wahb narrated to us, Hisham ibn Sa’d informed me, from Zayd ibn Aslam, from ‘Ata’ ibn Yasar, from Abu Sa’id al-Khudri: That he entered upon the Messenger of Allah (may Allah bless him and grant him peace) while he was suffering from a fever, and he was covered with a velvet blanket. He placed his hand upon him and felt its heat above the blanket. Abu Sa’id said, "How intense is the heat of your fever, O Messenger of Allah!" The Messenger of Allah (may Allah bless him and grant him peace) said, "We are like that; the affliction is intensified upon us, and the reward is doubled for us." We said, "O Messenger of Allah, who are the people most severely afflicted?" He said, "The prophets and the righteous. Indeed, one of them would be afflicted with poverty until he would find nothing but a cloak to wrap himself in and wear, and he would be afflicted with lice until it killed him. And one of them would be more joyful with the affliction than you are with a gift."