Things for which Wudhu is obligatory

322. It is obligatory to perform Wudhu for the following six things:

For all obligatory prayers, except Namaz-e-Mayyit[1]. As regards Mustahab prayers, Wudhu is a condition for their validity.
For the Sajdah and Tashahhud which a person forgot to perform during the prayers, provided that he invalidated his Wudhu, for example by urinating, after Namaz, and before performing those forgotten acts. Moreover, as per obligatory precaution, it is necessary to perform Wudhu for Sajdatus sahw.
For the obligatory Tawaf of the Holy Ka'bah.
If a person has made a Nadhr, or a solemn pledge, or taken an oath for Wudhu.
If a person has made a Nadhr to touch the written script of the Holy Qur'an.
For washing and making Pak the Holy Qur'an which has become Najis, or for taking it out from a place where its being is considered a desecration, when he becomes obliged to touch the script of the holy Qur'an with his hand, or some other part of his body. But if the delay by making Wudhu causes further desecration of the holy Qur'an, one should take it out and make it Pak, without performing Wudhu.

323. It is Haraam to touch the script of the holy Qur'an with any part of one's body, without performing Wudhu, and as per recommended precaution, one should not touch the script of the Holy Qur'an even with his hair. However, there is no harm in touching the translation of the holy Qur'an, in Persian or in any other language, without Wudhu.

324. It is not obligatory to prevent a child or an insane person from touching the script of the holy Qur'an. However, if their touching the holy Qur'an violates its sanctity, they should be prevented from touching it.

325. It is Haraam to touch the Name of Allah without Wudhu, in whichever language they may have been written. Moreover, as per obligatory precaution, it is better not

to touch, without Wudhu, the name of the holy Prophet of Islam, the holy Imams and Lady Fatima Zahra (peace be upon them).

326. If a person performs Wudhu or Ghusl before the time for prayers, in order to be in state of purity, they will be deemed valid. And even if he performs Wudhu near the time of Namaz, with the Niyyat (intention) of preparing himself for Namaz, there is no objection.

327. If a person believes that the time for prayers has set in, and makes the Niyyat of Wajib Wudhu, and then realizes after performing the Wudhu that the time for the prayers had not set in, his Wudhu is in order.

328. Wudhu is Mustahab for the following purposes:

Namaz-e-Mayyit.
Visiting the graves.
Entering a Masjid.
Entering the Shrines of the holy Prophets and Imams (A.S.).
For reading, writing, or touching the margin or border of the holy Qur'an, or for keeping it with oneself.
Before going to bed for sleep. It is also Mustahab that a person already in Wudhu should perform a fresh Wudhu for every Namaz.

If he has performed Wudhu for any one of the above purposes, he can commit all acts which require Wudhu. For example, he can even pray with that Wudhu.

[1] A prayer which is prayed on a dead body for his repentance.