"I arrived upon the Messenger of Allah (ﷺ) at Khaibar along with a group of the Ash'ari tribe. He gave us shared along with those that conquered it." This Hadith is Hasan Sahih Gharib. This is acted upon according to some of the people of knowledge. Al-Awza'i said: "Whoever meets up with the Muslims before the horses, share is distributed, then he is given a share." And Buraid's (a narrator) Kunyah is Abu Buraidah and he is trustworthy. Sufyan Ath-Thawri, Ibn 'Uyainah and others report from him.
حَدَّثَنَا أَبُو سَعِيدٍ الأَشَجُّ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ، حَدَّثَنَا بُرَيْدُ بْنُ عَبْدِ اللَّهِ بْنِ أَبِي بُرْدَةَ، عَنْ جَدِّهِ أَبِي بُرْدَةَ، عَنْ أَبِي مُوسَى، قَالَ قَدِمْتُ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فِي نَفَرٍ مِنَ الأَشْعَرِيِّينَ خَيْبَرَ فَأَسْهَمَ لَنَا مَعَ الَّذِينَ افْتَتَحُوهَا . هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ . وَالْعَمَلُ عَلَى هَذَا عِنْدَ بَعْضِ أَهْلِ الْعِلْمِ قَالَ الأَوْزَاعِيُّ مَنْ لَحِقَ بِالْمُسْلِمِينَ قَبْلَ أَنْ يُسْهَمَ لِلْخَيْلِ أُسْهِمَ لَهُ . وَبُرَيْدٌ يُكْنَى أَبَا بُرَيْدَةَ وَهُوَ ثِقَةٌ وَرَوَى عَنْهُ سُفْيَانُ الثَّوْرِيُّ وَابْنُ عُيَيْنَةَ وَغَيْرُهُمَا .
Tirmizi
The Book on Military Expeditions • Hadith 1597