The scholars differ over what exactly constitutes a few motions and what constitutes many motions. Some say that one makes many motions when, if seen from behind, one would be certain that he was not performing salah, and anything less than that amount is considered only a few motions. Some say that it is any act or string of actions which would make others believe that the person is not praying.
An-Nawawi says: “If a person performs a lot of actions that are not part of the salah, he invalidates his salah, and, on this point, there is no difference of opinion. If the acts are few, then they do not invalidate the salah and, on this point, there also is no difference of opinion. This is the exact position. However, there does exist a difference of opinion over what exactly constitutes a few actions and many actions, [and there exist four opinions on this point…” He says that the fourth opinion is the correct and most popular opinion. The fourth opinion is that the exact definitions of too much and too little are determined by generally accepted standards. One is not harmed in his salah by common acts such as nodding in reply to a salutation, taking off one’s shoes, raising the headdress and putting it back in place, putting on or taking off a light garment, carrying or holding a small child, preventing someone from passing in front of the person in prayer, covering one’s spittle in one’s clothing and similar other actions. As for the other acts, those which are considered to constitute many actions (e.g., taking many consecutive steps, performing actions repeatedly) they invalidate the prayer. An-Nawawi also says: “The scholars are in agreement that many actions invalidate the prayer if they are performed consecutively [i.e., one after another]. If one separates the actions, for instance, taking a step and then stopping for a while, then taking another step or two, and then another two steps, after a pause (though a short one) between them, then the salah will not be harmed, even if he (in this manner should take a hundred or more steps. There is no difference of opinion on this point. As for light actions,” he continues, “such as, moving one’s finger in glorifying Allah or in itching, and so forth., these do not invalidate the prayer according to the well-known, authentic opinion, even when they are done repeatedly and consecutively, but they are disliked.” AshShaf’i, in a statement concerning it, says: “Even if one counts the verses on one’s fingers, it would not invalidate one’s salah, but it is best to avoid [such an act].”