When 'Amr came back, Banu Ma'mar came to him and they referred their dispute with him concerning the wala' of their sister to 'Umar. 'Umar ؓ said, I will judge between you according to what I heard from the Messenger of Allah ﷺ . I heard him say: “What the son or father acquires goes to his agnates, no matter who they are.” So he ruled in our favour,
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ مَا أَحْرَزَ الْوَلَدُ أَوِ الْوَالِدُ فَهُوَ لِعَصَبَتِهِ مَنْ كَانَ فَقَضَى لَنَا بِهِ