رَجَعَ الْمُسَافِرُونَ فَرِحِينَ
Translation: The travelers returned happy.
رَجَعَ: past verb.
الْمُسَافِرُونَ: subject, nominative with wāw.
فَرِحِينَ: ḥāl, accusative with yāʾ, sound masculine plural.
Distinguish plurality agreement from the morphological case marker.