Answer: The obligatory acts of ablution are the acts that render one’s ablution invalid if one of them is left out. They are:

1. Washing the face, which includes rinsing the mouth and sniffing water into the nose

2. Washing the arms including the elbows

3. Wiping over the head, which includes wiping the ears

4. Washing the feet up to the ankles

5. Maintaining the prescribed order by washing the face first, followed by the hands, then wiping over the head, and finally washing the feet.

6. Succession, which means washing the organs of ablution successively without leaving an interval of time that allows the organs to become dry.

An example in this regard is when one performs only half of the ablution and then completes it some other time. In this case, one’s ablution is invalid.