Ibn Hibban

Abdullah bin Dinar narrates: I and Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) were present near a house in the market of Khalid bin Utbah. There a man came and wanted to speak in secret with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both). At that time, besides me and that man, there was no one else with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) who wanted to speak with him in secret. So Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) called another person, until we became four people. Then he said to me and to the person whom he had called: "You both move aside." I heard the Noble Prophet (peace and blessings be upon him) say: "Two people should not converse secretly excluding a third."