Answered by Shaykh Faraz Rabbani
What is considered to be excessive movement in salat? Have the ulema quantified this? i.e.. Is there a certain amount of unnecessary joint movement after which the salat becomes invalid?

Walaikum assalam,
The soundest opinion, as mentioned by Ibn Abidin in his Hashiya, is that “excessive movement” is:
– Such that someone looking on from a distance would NOT doubt that you are NOT praying, if he didn’t know beforehand that you were. If unsure whether it is excessive, then it is not.
Another opinion is that 3 consecutive movements are excessive. Though this is not the soundest opinion, it sheds light on what IS usually excessive.
Wassalam,
Faraz.