It was narrated from ‘Ubadah bin Samit that the Prophet ﷺ awarded one quarter of the spoils to those who attacked the enemy at the beginning and one third to those who attacked at the end.
أَنَّ النَّبِيَّ ﷺ نَفَّلَ فِي الْبَدْأَةِ الرُّبُعَ وَفِي الرَّجْعَةِ الثُّلُثَ