Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: "(On the occasion of Badr,) the companions of the Prophet (peace and blessings be upon him) numbered (about) three hundred."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains Yahya bin Abd al-Hamid al-Himmani, and he is da'if (weak).