What is the ruling on performing obligatory prayers with a Mustahabb (recommended) Wudu', such as Wudu' before sleep, and what are the views of the four Madhhabs and their evidence on this matter?

If a person performs ablution (wudu') for an act for which purity is recommended (sunnah), such as sleep or reciting the Qur'an, there is a difference of opinion regarding whether his ritual impurity (hadath) is removed:

First View: His ritual impurity is not removed. This is the madhhab of the Malikis and Shafi'is. Al-Mazari said: "The action he intended is valid even with the persistence of ritual impurity, so his intention did not entail the removal of impurity." Al-Nawawi said: "The most correct view is that it is not valid."

Second View: His ritual impurity is removed. This is the madhhab of the Hanafis and Hanbalis, and one view among the Shafi'is. The Hanafis do not stipulate intention for the removal of ritual impurity at all. As for the Hanbalis, they believe that whoever intends purity for an act for which it is recommended has his ritual impurity removed. The argument of those who permit prayer with this ablution is that it entails the removal of ritual impurity; otherwise, it would be of no benefit, as he performs ablution to sleep in a state of purity.