Is doubting the recitation of Al-Fatiha during prayer or doubting one's ablution while performing it considered hesitation in worship, and does it invalidate it?

There are two types of doubt:

1. Doubt of the one afflicted with obsessive whispers (waswasa): This type of doubt is to be ignored. One must turn away from doubts and whispers, as Sheikh Ibn 'Uthaymeen said: "And doubt after the act does not affect... and similarly if doubts become frequent."

2. Normal doubt for one not afflicted with obsessive whispers: If one doubts during an act of worship whether they have performed a part of it, the default is that they have not performed it. They must then go back and perform what they doubted to make their worship valid. For example, if one doubts washing their face during ablution, they must wash it. Ibn Qasim said: "As for before completion [of the act of worship], it is like one who has not performed what they doubted, unless it is a mere illusion like waswasa, in which case it is to be disregarded."