From Issue: 500 [Read full issue]
Intention and Intention
Any deed performed with the sole intention of pleasing Allah which is also consistent with His shariah is an act of worship or ibadah. At the same time, though, there are some deeds that must be accompanied with an intention for them to be accepted by Allah. These deeds include, according to the majority opinion, ablution, ghusl, tayammum, prayers, zakat, fasts, pilgrimage, itikaf and other acts of worship.
For example, someone could go the entire day without eating due to lack of food or for health reasons but this would not be the same thing as fasting as an act of worship. Whenever anyone wishes to fast as an act of worship, one must first make the intention to perform that act of worship. Therefore, in order to distinguish the act of worship from any other customary act, the intention must be present in the heart of the person.
"Commentary on the Forty Hadith of al-Nawawi" - Jamaal al-Din M. Zarabozo, p. 141