How much movement invalidates the prayer?

Answer

The believer must be still in the prayer. The Messenger ﷺ said: Be still in the prayer. Allah says: ﴿قَدْ أَفْلَحَ الْمُؤْمِنُونَ ۝﴾ "Successful indeed are the believers" those who are humble in their prayer [al-Muʾminūn: 1, 2].

So the one praying must be still and humble in his prayer, and avoid the excessive movement that invalidates it and makes him as though he were not praying. A small amount is excused. But when the movements are many and continuous, they invalidate the prayer according to all the scholars. One must therefore be careful.

If a person sees excessive movement in his brother, he should advise him and direct him to what is good, even by a gesture during the prayer. After the prayer he advises him in words; during the prayer, by a gesture, so that he becomes aware of himself and gives up these habits he has formed.

As for few and scattered movements, they are excused. The Prophet ﷺ prayed while carrying Umāmah: when he prostrated he put her down, and when he stood he picked her up, ʿalayhi al-ṣalātu wa-l-salām. He opened the door for ʿĀʾishah. In the eclipse prayer he stepped forward, moving forward into the rows, until he reached out for a cluster of fruit when Paradise was shown to him, but it was not decreed that he should take it. When the Fire was shown to him, he stepped back, and the rows stepped back.

So the small amount that happens to a person is excused, but many movements in succession invalidate the prayer. There is no fixed number for them. Some set the limit at three movements, but this has no basis. The limit is simply that they are many: when they are many by common custom and continuous, they invalidate the prayer; when they are scattered, they do not.

Answer

In all of them — in the bowing, the prostration or the standing — there is no fixed limit.