What is the legal "cause" (Sabab) of Wudu as defined in Noor-ul-Idah?

Ablution (الوضوء): Conditions of Obligation and Validity

• The arrival of Friday morning.
• The desire to render permissible acts that are forbidden without purification, such as prayer.
• Purely to cool down in hot weather.
• Entering a market or a business center.