ENOfficial
It was narrated that Bara’ bin ‘Azib said: “We were talking about how, on the Day of Badr, the Companions of the Messenger of Allah (ﷺ) numbered three hundred ten and something, the same number as the Companions of (Talut) who crossed the river with him, and no one crossed the river with him but a believer.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا أَبُو عَامِرٍ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْبَرَاءِ بْنِ عَازِبٍ، قَالَ كُنَّا نَتَحَدَّثُ أَنَّ أَصْحَابَ، رَسُولِ اللَّهِ صلى الله عليه وسلم كَانُوا يَوْمَ بَدْرٍ ثَلاَثَمِائَةٍ وَبِضْعَةَ عَشَرَ عَلَى عِدَّةِ أَصْحَابِ طَالُوتَ مَنْ جَازَ مَعَهُ النَّهَرَ وَمَا جَازَ مَعَهُ إِلاَّ مُؤْمِنٌ .
sunnah.com