Abdullah bin Umar reported,

He was with the Messenger of Allah ﷺ one day along with a group of his companions, and among what he said to them was, "Part of obedience to Allah is that you obey me, and part of obedience to me is that you obey your leaders. If they pray sitting, then all of you pray sitting."

Azami 2284

Sahih

عن ابن عمر

أنه كان يوما من الأيام عند رسول الله ﷺ وفي نفر من أصحابه فمما قال لهم: فإن من طاعة الله أن تطيعوني، وإن من طاعتي أن تطيعوا أئمتكم، فإن صلوا قعودا فصلوا قعودا أجمعين.

الأعظمي 2284صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Prayer
Chapter
Leadership
Section
When the imam prays sitting, they should pray sitting
Numbering
Jami al-Kamil 2284 (2nd edition)
Azami 2284