Musannaf Ibn Abi Shaybah 8378 — Those who used to shorten the prayer

Ibn Abi Layla said: Sayyiduna Salman (may Allah be pleased with him) set out on a military expedition in a group of thirteen men from the Companions of the Messenger of Allah (peace and blessings be upon him), and he was the oldest of them all. When the time of prayer came, they all said: O Abu Abdullah! You lead the prayer. He said: I do not have the right to lead the prayer; you are Arabs and the Prophet (peace and blessings be upon him) is from among you. So let one of you step forward and lead the prayer. At this one of them stepped forward and prayed four rak'ahs with them. When we had finished the prayer, Sayyiduna Salman said: Why should we pray four rak'ahs? Two rak'ahs, half of the four, are sufficient for us.