Sayyiduna Imran bin Husayn (may Allah be pleased with him) narrates that we were on a journey with the Messenger of Allah (peace and blessings be upon him) when he led the people in prayer. When the prayer was finished, (he saw) a man sitting apart who had not prayed with the people. The Messenger of Allah (peace and blessings be upon him) asked: "So-and-so! Why did you not pray with the people?" He replied: "O Messenger of Allah! I became junub (in a state of major ritual impurity) and water is not available." The Prophet (peace and blessings be upon him) said: "Use earth (for tayammum), that is sufficient."