Wudu' (Ablution) and Tayammum (Dry Ablution)

Wudu:
Wudu is the Islamic act of washing parts of the body using water. Muslims are required to perform wudu in preparation for ritual prayers and for handling and reading the Qur'an. Wudu is often translated as "partial ablution", as opposed to ghusl, or "full ablution".

Allah (SWA) says in the Qur’an: “Oh you who believe, when you prepare for As-Salah, wash your faces and your hand to the elbows; rub your heads and wash your feet up to the ankles.  And if you are unclean, purify yourself”.  (Suratul Ma idah 5:6).
 

There are four things fard in wudu’:
1. Washing the face from the forehead to the lower portion of the chin and from one ear to the other;
2. Washing both the arms, up to the elbows.
3. Performing Masah of one fourth of the head .
4.Washing of both feet up to the ankles. It's not sufficient for one to pass wet hand over the feet or shoes. Under certain conditions masah can be done over leather socks known as khuffs.

There are also the Sunnah (Practice) of the Prophet Muhammad (Pbuh):
1. Niyyah (intention);
2. Reciting Bismillah.
3. Washing the hands three times up to the wrists and making sure that water has reached between the fingers.
4. Brushing the teeth by miswaak or fingers.
5. Gargling three times.
6. Sniff water into the nostrils three times to clean them and then wash the tip of the nose.
7. Khilaal – i.e. to pass wet fingers into the beard.
8. Passing wet hands over the whole head and around the ears.
9. Passing of fingers between the fingers of the hand and feet.
10. Washing each limb thrice.

Mustahab of wudu’:
A handful of mustahab (recommended) acts that are considered to make the wudu better. If one of these acts is omitted, the wudu is still considered valid.

1. Reciting the shahadah after the ablution.
2. There should be no delay between washing two limbs.
3. During wudu one should not engage in worldly talk.
4. Choosing a clean place for ablution.
5. Not wasting water in ablution.

Four things are makrooh in wudu’:
1. Doing wuduu’ at a dirty place;
2. Cleaning the nose with the right hand;
3.Talking unnecessarily while doing wuduu’; and
4.Doing wuduu’ in a way that is against the sunnah.

Performance of wudu:
1. Start by making niyyah (intention) to perform wudu and cleanse the self of impurities.
2. Say bismillah ("In the Name of Allah (God)").
3. Wash the right hand up to the wrist (and between the fingers) three times, then similarly for the left hand.
4. Rinse the mouth and spit out the water three times and rub the teeth with a Miswak. If Miswak is not available then one should use the finger.
5. Gently put water into the nostrils with the right hand, pinch the top of the nose with the left hand to exhale the water. This is performed three times.
6. Wash the face (from the hairline on the forehead to where facial hair begins and ear to ear). This is to be performed three times.
7. Wash the entire right arm, including the hand, up to and including the elbow three times; then the left arm three times. Pass fingers of one hand between the fingers of the other hand. If wearing a ring it should be moved freely to allow water to pass under it.
8. Then perform Masah. Wet hands should be passed all over the head; then the first finger of the right and left hand should be moved in the right and left ears respectively and in the same operation thumbs should be passed around the ears; then pass the backs of the hands over the hind part of the neck only. Hands should not be passed around the fore-neck as it is prohibited. This is only done once. One may NOT make masah over a Muslim head cap. Fresh water need not be taken for performing the masah of the ears.
9. Starting with the right foot, wash both feet from the toes up to and including the ankles thrice. The little finger of te left hand should be passed between the fingers of both the feet beginning from the little toe of the right foot and ending with the little toe of the left foot.
10. Recite the shahadah.

Invalidation of wudu:
Theoretically, one can perform one wudu for fajr salaat and this wudu would be considered valid for the rest of the day. However, certain things invalidate the wudu (often referred to as "breaking wudu") and these can be stated generically thus:

1. Defecation, passing gas or urination.
2. Emission of semen.
3. Sleep.
4. Passing blood.
5. Vomiting.
6. Loss of senses.
7. Fainting
8. laughing aloud whilst in Namaaz.

Tayammum:
Tayammum  refers to the dry ablution in Islam using sand or dust, which may be performed in place of wudu or ghusl, only if no clean water is readily available.

Circumstances when Tayammum is necessary:
Tayammum becomes necessary in place of wudu or ghusl when one of the following circumstances prevails:
1. When there is no water.
2. When water is scarce.
3. When it is dangerous to go to a place where there is water.
4. When water is located very far away.
5. During illness, when washing with water will increase the illness or delay recovery.

Performing Tayammum:
Tayammum consists of the following steps:

1. Finding a piece of ground which is free of najaasah. This could be any natural surface such as rock, sand, dust, grass.
2. Recite the bismillah.
3. Make niya, or intention to make tayammum.
4. Place the hands on the surface of the ground.
5. Lift hands with palms downwards, ensuring that no dust remains, may rub them together
6. Rub face with hands.
7. Press hands to ground and touch sides of hands together.
8. Rub right arm with left hand, from the fingers to the elbow, and back along the inner arm to the hand. Do the same with the other arm.

The same conditions that invalidate wudu also invalidate tayammum. In addition, a person's tayammum is invalidated as and when water becomes available.

Historical controversy:
Umar denied that tayammum could constitute ghusl, although the Qur'an explicitly says it can, and even though Ammar ibn Yasir reminded him that it was Sunnah. Although it's legality is no longer in dispute, the historical controversy is regularly mentioned in Shi'a - Sunni debates.