Umm Fadhl (RA) narrated:

The Prophet of Allah (SWT) went to visit a man, and he complained about his illness and wished to die. The Prophet of Islam (PBUH) told him:  Do not wish for death, because if you are a good-doer, by being alive your good deeds are increased; and if you are a sinner you will be given time to repent from your sins; so do not wish for death [1].

[1] Amali Toosi, Majlis Sizdahum, Page 385.

Source:en.shafaqna.com