Once, Sayyiduna Ibn Mas'ud (may Allah be pleased with him) went to the house of Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him). When the time for prayer came, Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) said: O Abu Abdur Rahman! Please step forward, for you are greater than us in knowledge and also older in age. He replied: No! You step forward, as we have come to your house and your mosque, therefore you have more right. Thus, Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) stepped forward and took off his shoes. When the prayer ended and he finished with salam, Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: What was the need to take off the shoes? Were we in a sacred valley? I have seen the Prophet (peace and blessings of Allah be upon him) praying in leather socks and shoes.