The Messenger of Allah ﷺ said, "Whoever follows a funeral procession should not sit down until the bier is placed on the ground."
حدثنا علي بن عاصم قال أخبرني سهيل بن أبي صالح عن أبيه
قال رسول الله ﷺ من تبع جنازة فلا يجلس حتى توضع
Its isnad is sahih, and the hadith has already appeared at 11267.