The Messenger of Allah ﷺ said, "When one of you sees a funeral procession, let him stand until it passes him or is set down."
حدثنا عبد الرزاق حدثنا معمر عن الزهري عن سالم عن ابن عمر
قال رسول الله ﷺ إذا رأى أحدكم الجنازة فليقم حتى تخلفه أو توضع
Its isnad is sahih, its narrators are leading authorities, and it has already appeared at 15614.