Is the intention (Niyyah) to shorten the prayer a required condition for its permissibility?
Chapter on the Traveler's Prayer
Al-Mughni
Book of Prayer
Primary text
The intention to shorten the prayer is a necessary condition for its validity, and this intention must exist at the beginning of the prayer, similar to the intention for performing the prayer itself. This is the view adopted by Al-Khiraqi and chosen by Al-Qadi. The evidence supporting this is that completing the prayer in full is the default state (Al-Asl), and the concession of shortening requires a specific designation (the intention) to deviate from this default.
Supporting text
Abu Bakr argued that intention is not required because whatever is good in an act of worship before entering it is also good after entering it, similar to fasting. Furthermore, shortening is the original state (Al-Asl) supported by narrations from 'Aisha, 'Umar, and Ibn Abbas, thus requiring no specific intention, like completing the prayer while resident. If a person doubts during the prayer whether they formed the intention to shorten at the beginning, they must complete the prayer fully as a precautionary measure because the default is the absence of the intention to shorten.