The Prophet ﷺ gave az-Zubayr the land as a fief up to the reach of his horse when he runs. He, therefore, made his horse run until it stopped. He then threw his flog. Thereupon he said: Give him (the land) up to the point where his flog has reached. (Using translation from Abū Dāʾūd 3072)
أَنَّ النَّبِيَّ ﷺ أَقْطَعَ الزُّبَيْرَ حُضْرَ فَرَسِهِ بِأَرْضٍيُقَالُ لَهَا ثُرَيْرٌ فَأَجْرَى الْفَرَسَ حَتَّى قَامَ ثُمَّ رَمَى بِسَوْطِهِ فَقَالَ أَعْطُوهُ حَيْثُ بَلَغَ السَّوْطُ