Musannaf Ibn Abi Shaybah 11123 — Reports on the reward for fever

It is narrated from Ata bin Yasar that the Prophet (peace and blessings be upon him) said: "When a believing servant falls ill, Allah Almighty commands the Noble Scribes: Write for My servant the like of what he used to do while healthy, until I take him to Myself or grant him relief from this hardship."