The Messenger of Allah said: "Whenever you see a funeral (procession), stand up (for it). Whoever follows it, then do not sit down until it is put down."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا رَأَيْتُمُ الْجَنَازَةَ فَقُومُوا لَهَا فَمَنْ تَبِعَهَا فَلاَ يَقْعُدَنَّ حَتَّى تُوضَعَ