There is a common practice to rise on one’s heels three times at the completion of Shemoneh Esrei, after one has taken his or her three steps back and forward. Put simply, there is absolutely no source for this practice.
Unlike similar things discussed in this series, and elsewhere, that often might have one or two obscure sources, bouncing at the end of Shemoneh Esrei really has absolutely no source. It’s not mentioned in any halachic work, primary or otherwise. It is not spoken about in the Shulchan Aruch, Rama, Aruch HaShulchan, Mishneh Brurah, Tur, Rambam, or anywhere else for that matter. This is so much the case, in fact, that seforim like Minhagei Yisrael — the sole purpose of which is to find a source, no matter its obscurity, for every custom of the Jewish people — state that there is simply no source for this practice.
There is, however, a rather popular theory as to how the practice most probably developed. After taking your three steps back and bowing at the completion of Shemoneh Esrei, it is considered more proper to wait in place until the chazan gets up to kedusha. It is at that point that one should take his or her three steps forward as kedusha is starting. Most likely, people witnessed Rabbis, Roshei Yeshivah, and so forth, taking their three steps forward just in time for the “kadosh, kadosh, kadosh” of kedusha during which one is indeed supposed to bounce on their heels. People incorrectly assumed that the bouncing was tied to the three steps forward, and not to kedusha — and the rest, as they say, is history.
This is another example of an erroneous practice that isn’t really harmful, and as such, should not be made too big a deal out of. That being said, those that know ought not continue practices that have no source, as we should not be adding erroneous and unnecessary laws and customs to halacha. On the one hand, it is simply improper, as over time it leads to distortion and corruption of the law. On the other hand, halacha is all-encompassing, complicated, and difficult enough to follow properly as it is that we need not spend even the smallest amount of energy doing things without reason.
A few conclusory notes:
- The reason why one is allowed to take his or her three steps forward during the start of kedusha is because the opening clause of kedusha is really just an introduction — a call to action — and does not have the full status of kedusha. As such, one can still move to his or her place during this line.
- There is also little to no source for bowing right and left as the words “וְקָרָא זֶה אֶל זֶה וְאָמַר” are said.
- The Kitzur Shulchan Aruch (18:12) writes that one should not take more than the requisite 3 steps back (nor should they be overly large steps), most likely because this is seen as arrogant.