Musnad Ahmad 28:394

'Abd al-Razzaq narrated to us, Sufyan informed us, from 'Alqamah ibn Marthad, from al-Qasim ibn Mukhaymirah, from 'Abdullah ibn 'Amr, who said: The Prophet, may Allah bless him and grant him peace, said: "There is no one among the Muslims who is afflicted with a trial in his body, except that Allah the Exalted commands the guardians who guard him, saying: 'Write for My servant, in every day and night, the like of what he used to do of good, as long as he is confined in My bonds.'"