Purification from impurity is a condition of prayer being accepted; no prayer is valid without one being in a state of purity. In this hadith, Abu Hurayrah (may Allah be pleased with him) tells us that one day the iqamah was given for one of the prayers in the mosque of the Messenger of Allah (blessings and peace of Allah be upon him), and the rows were organized and straightened as the people stood for prayer. The Prophet (blessings and peace of Allah be upon him) came out to lead the people in prayer, but when he stood in the imam’s place, he remembered that he was junub and had not done ghusl to cleanse himself from janabah. The word janabah refers to anyone who emits maniy (semen) or has intercourse; it is so called because he must avoid (ijtinab) prayer and other acts of worship until he has purified himself. So the Prophet (blessings and peace of Allah be upon him) instructed his companions (may Allah be pleased with them) to remain where they were, then he went back to the apartments of his wives and did ghusl, then he came out to them with his head dripping with water as a result of having done ghusl. Then he led the people in prayer. This was by way of teaching his companions and his ummah that no one should be embarrassed about acts of purification and doing what Allah has prescribed when he remembers it, and he should not feel embarrassed before people. The hadith indicates that the one who remembers that he is junub when he is in the mosque should leave the mosque and do ghusl; he does not have to do tayammum in order to walk out of the mosque, and the same applies to the one who wants to pass through the mosque when he is junub..