Tayammum is done as a substitution for water. Allah said in the Qur'an: “…and (if) you find no water, then perform Tayammum with good earth, wiping your faces and hands with it.” (Qur'an, 5:6) The Prophet (peace be upon him) said: “The earth was made a masjid (place of prayer) and purity for me.” (Al-Bukhari and Muslim) It is permissible to perform Tayammum with all types of earth such as sand, dust etc. This applies even if the earth is a smooth and there is no sand or dust found on it. It is permissible to perform Tayammum on such a type of land. The evidence for this is what has been reported by Jabir (may Allah be pleased with him) that the Prophet (peace be upon him) said: “The earth was made a masjid (place of prayer) and a purity for me. So any man from my ummah (nation) who has the time for prayer come upon him, then let him pray, for he has his place of prayer and his purifier with him. So if the prayer time comes upon him and he is in a land in which there is sand or the prayer time comes upon him and he is in a smooth surfaced land, then in this situation, he is ordered to perform Tayammum with this earth.” (Al-Bukhari and Muslim) A person can pray – obligatory or voluntary prayers – with Tayammum. The ruling that Tayammum takes is similar to (wudhu with) water. So whatever nullifies one's wudhu, then it also nullifies and renders void one's Tayammum. However, if water is found (and one has Tayammum), something extra is required. It becomes obligatory on this person to make wudhu with water even if his Tayammum hasn't been nullified by one of the factors that cancel out wudhu. This is based on the hadith of Abu Hurairah (may Allah be pleased with him) who said: “Allah's Messenger (peace be upon him) said: “The earth serves as the wudhu of the Muslim even if he doesn't find water for 10 years. But if he finds water, then he should fear Allah and let his skin touch it.” This hadith was reported by Al-Bazaar and it has a supporting witness from a similar narration of Abu Dharr. The person, however, does not have to repeat the prayers he performed while using that Tayammum. The description of Tayammum, is that one must first make his intention based on the hadith: “Verily, actions are only by intentions.” He must mention the name of Allah (saying Bismillah) and strike the earth with his two hands one time and then wipe the palms together along with the back of each hand and his face. This is based on the hadith of Ammar Bin Yasir: “He (i.e. Allah's Messenger) struck the earth one time and then wiped his left palm on his right palm, the back of his hands and his face.” (Al-Bukhari and Muslim) – transcribed from his lecture on Salah/SG Tayammum is permitted in two situations: 1. When there is no water to be found. 2. When one is not able to use water due to sickness and so on. Tayammum can be performed for both types of ritual impurities (hadath): 1. Minor impurity such as passing urine or stool. 2. Major Impurity such as sexual relations or semen ejaculation. __
