107. Communicating During Shemoneh Esrei

18:13 When one takes his three steps back at the end of Shemoneh Esrei, he continues to stand with his feet together. One should not turn to face the west (namely, facing the congregation – MB 123:12) or return to his place until the shaliach tzibbur has reached Kedusha. (If the one praying takes longer than the shaliach tzibbur and Kedusha is already underway by the time he finishes, he can take his three steps forward and join Kedusha in progress – MB123:9.) A person who is praying alone should also wait this length of time. If the shul is crowded, one may return to his place when the shaliach tzibbur begins the repetition of Shemoneh Esrei, though one should still wait the amount of time it would take to walk four cubits (six feet – see Mishnah Brurah 123:11).

18:14 During Shemoneh Esrei, one may not communicate by gesturing, winking or silently mouthing words; he may not even interrupt in order to answer Kaddish, Kedusha and Barchu. Rather, one must silently pay attention to what the chazzan and the congregation are saying. Doing so is considered as if he answered these prayers without interrupting Shemoneh Esrei.