Following things terminate a person’s Wudū:
1. A seminal/ovular discharge.
2. Sexual intercourse, whether the discharge or the
ejaculation occurs or not.
3. Pre-seminal discharge (spermatorrhea).
4. Passing of bowels.
5. Passing of wind.
6. Passing of urine.
Of this the first two require Ghusl (bath), and the last
five mere Wudū to make a person pure.
This is all as far as the Sharī‘ah is concerned in this
regard. It spells out that only these six factors terminate a person’s Wudū.
However, there may be other instances apart from these six
which may make a person feel impure and unclean, and which depend on how
sensitive a person is in matters of cleanliness. The Prophet’s own sensitivity
in this regard made him do Wudū at such instances. But, he never made them
compulsory for his followers. For example, after eating a camel’s meat, he is
reported to have done Wudū. Similarly, he once said that if a person touches his
private parts he should do Wudū. Therefore, one must not mix up the
desirable/permissible with the compulsory.
Sleep itself does not terminate a person’s Wudū. However,
since during sleep a person loses consciousness, there is a possibility that he
might have encountered some of the factors that terminate Wudū without his
knowing them. Therefore, as a precautionary measure, it is desirable that a
person do Wudū. Furthermore, if a person just doses off or wakes up from a sleep
and is certain that he is still in his state of Wudū, he does not need to do it
again. It is reported:
The Companions of the Prophet (sws) would go to sleep.
Then would wake up and offer Salāh without doing Wudū. (Tirmadhī, Kitāb al-Tahārah)
Merely seeing someone naked does not terminate one's Wudū
unless of course there is some sort of a seminal discharge.