If The Imam Experiences An Excuse, From Illness, Or Travelling, Etc. He May Appoint Someone Else To Lead The People In Prayer; The One Who Offers Prayer Behind The Imam Sitting Because He Is Unable To Stand Must Stand If He Is Able To Do So; And The Abrogation Of Sitting Behind A Sitting Imam For Those Who Are Able To Stand Sahih Muslim 419 b
Translation
Anas reported
The last glance that I have had of the Messenger of Allah (ﷺ) (before his death) was that when he on Monday drew the curtain aside. The hadith transmitted by Salih is perfect and complete.