Yahya related to me from Malik from Zayd ibn Aslam from Ata ibn
Yasar that the Messenger of Allah, may Allah bless him and grant him
peace, said, "When the slave is ill, Allah ta'ala sends two angels to
him." He said, "They look at what he says to his visitors. If he
praises Allah and lauds Him, when they come to him, they take that up
to Allah, the Mighty, the Majestic, and He knows best, and He says,
'If I make my slave die, I will make him enter the Garden. If I heal
him, I will replace his flesh with better flesh and his blood with
better blood and I will efface his evil actions.'"
Muwatta Malik Book 50, Hadith 5