Musnad Ahmad 31:568

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Abu Salih, from Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Prophet will come on the Day of Resurrection, and with him will be one man, and the Prophet with whom will be two men, and more than that. His people will be summoned, and it will be said to them: 'Did this one convey [the message] to you?' They will say: 'No.' It will be said to him: 'Did you convey [the message] to your people?' He will say: 'Yes.' It will be said to him: 'Who will testify for you?' He will say: 'Muhammad and his nation.' So he and his nation will be summoned, and it will be said to them: 'Did this one convey [the message] to his people?' They will say: 'Yes.' It will be said: 'And what is your knowledge [of that]?' They will say: 'Our Prophet came to us and informed us that the messengers had conveyed [the message].' That is the meaning of His saying: {And thus We have made you a just nation} [Al-Baqarah: 143]." He said: "He says: 'Just (fair/balanced).'" {...that you may be witnesses over the people and the Messenger may be a witness over you} [Al-Baqarah: 143].