ENOfficial
Narrated 'Amir bin Rabi`a: The Prophet (ﷺ) said, "If any one of you see a funeral procession and he is not going along with it, then he should stand and remain standing till he gets behind it, or it leaves him behind, or the coffin is put down before it goes ahead of him . "
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ عَنْ عَامِرِ بْنِ رَبِيعَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا رَأَى أَحَدُكُمْ جَنَازَةً فَإِنْ لَمْ يَكُنْ مَاشِيًا مَعَهَا فَلْيَقُمْ حَتَّى يُخَلِّفَهَا، أَوْ تُخَلِّفَهُ أَوْ تُوضَعَ مِنْ قَبْلِ أَنْ تُخَلِّفَهُ ".
sunnah.com