The Arabic word TAHAARAH (English: purification) denotes purity and cleanliness.
Allah commands Muslims to purify themselves outwardly from forbidden appearances and all types of physical impurities, and inwardly from the unpardonable sin of shirk as well as diseases of the heart such as envy, pride and hatred. Once they do so, they become worthy of His love, as the Qur’an states, “Allah loves those who turn to Him constantly and He loves those who keep themselves pure and clean.” Quran Surah Al-Baqarah, 2:222
Allah also commands them to purify themselves prior to standing before Him in prayer. If man generally cleans himself and puts on his finest clothes before meeting a person who has a worldly position of authority, such as being a king or a president, then, surely he has to do so before standing before the King of kings.
Allah commands Muslims to purify themselves and perform the partial ablution (wudoo’) before engaging in such ritual acts as performing the prayer(Salah). It is also recommended to perform wudoo’ before doing a number of things, for touching the Qur'an (according to some scholars it is obligatory and according to some other scholars it is Mustahab), for Tawaf (Circumambulation) of the Ka'bah (according to some scholars it is obligatory and according to some other scholars it is Mustahab) and sleep.
Therefore, before a Muslim offers a prayer(Salah), he must remove two things:
Najaasah - The Arabic word Najaasah denotes all physical substances which Islam considers impure and commands us to remove them before engaging in an act of worship.
If we want to pray, we must first remove all physical impurities from the body, clothing and the place where we intend to offer the prayer.
Physical impurity on the body, clothes, place where the prayer is intended to be performed, or anything or anywhere for that matter, can be removed with anything, be it water or otherwise, for Islam commands removing it. It is not stipulated as to how many times it must be washed off, except in the case of the physical impurity of a dog (i.e. its saliva, urine and faeces), where it must be washed seven times, one of which must be done with earth. For the rest of physical impurities, they must be washed off, and if some smell or stubborn stains remain after washing, they may be ignored. Once a woman asked the Prophet about washing off menstrual blood, and he said, “It would suffice to wash it off, and you do not have to worry about any stains that are left.” Sunan Abu Daawood: 365
A Muslim is recommended to enter the toilet with the left foot first after saying, Bismillaah. Allaahumma inneea‛oozu bika min-al-khubsi wal-khabaa’is (I seek refuge with You, O Allah, from the male and female jinn)
He is also recommended to leave the toilet with the right foot first and then say, “Ghufraanak”(I seek Your forgiveness, O Allah).
He must cover his private parts while answering the call of nature.
He must not answer the call of nature in a place where he may be seen or where he may offend people. Doing so is strictly forbidden
He must not face the qiblah, the direction of the Ka‛bah in Makkah towards which Muslims pray, or turn his back towards it, for the Prophet said, “When you are answering the call of nature, you should not face the qiblah or turn your back towards it.” Sahih Al-Bukhari: 386; Sahih Muslim: 264. This mainly applies if one is out in an open space. There is no harm, however, to do so in buildings, such as in present-day toilets.
He must try to be careful not to have any impurities splashed onto his body or clothes. If this happens accidentally, then one must wash the impurity off the affected place thoroughly.
Ritual impurity (Hadath) refers to the state of intangible uncleanliness that prevents a Muslim from offering the prayer until he removes it. It is not physical like najaasah.
This ritual impurity can be removed by performing the partial ablution (wudoo’) or a full ablution (ghusl /bath) using pure water.
Minor ritual impurity(Passing Urine or Motion/ stool): This can be removed by performing wudoo’ (ablution).
Major ritual impurity(Wet dream or Sexual intercourse between husband and wife): This can be removed by performing (Ghusl /Ritual bath).