Is it permissible to complete ablution after interrupting it to answer the the doorbell, or must one start anew?

Defining the criterion for muwalat (successive performance) in ablution is based on it being a condition for its validity. Scholars have differed in defining this criterion:

1. The Hanbalis hold that the criterion is not to delay washing a limb until the one before it has dried in a moderate climate. 2. There is also a narration from Imam Ahmad that the criterion is urf (custom), so whatever is considered a clear separation by custom is a separator, otherwise it is not.

Opening a door or similar actions are not considered a definitive break in muwalat, because they do not take a long time. However, if the separation is prolonged due to being preoccupied with another matter, then one must repeat the ablution from the beginning.