It is narrated from Hazrat Uqbah bin Aamir (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: There is no deed done throughout the day except that a seal is set upon it. So when a Muslim becomes ill, the angels present themselves before Allah and say, "O Lord! You have withheld so-and-so servant?" Allah Almighty says: "Keep sealing for him the deeds he used to do when he was healthy, until he recovers or passes away."
Hadith Referenceمسند احمد / مسند الشاميين / 17316
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن