Sunan Ibn Majah
1438
Daif+2

It was narrated from Abu Sa’eed Al-Khudri that the Messenger of Allah (ﷺ) said:“When you enter upon one who is sick, cheer him up and give him hope of a long life, for that does not change anything (of the Divine Decree), but it will cheer the heart of the one who is sick.”

DaifAl-Albani
DaifMuhammad Fouad Abd al-Baqi