If a person completes the Amida and is ready to take his three steps back and recite "Oseh Shalom," but somebody else is praying the Amida behind him, may he step back, or must he wait for the person behind him to complete the Amida?
The Halacha in this case depends on the distance between the two people. Halacha forbids passing within four Amot – approximately six feet – in front of a person while he prays the Amida. Therefore, if after taking his three steps one will be within four Amot of the person behind him, then he may not step back until the person behind him completes the Amida. If, however, he will still be beyond four Amot of the person behind him even after taking his three steps, then he may step back. Although the Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) held that one may not pass in front of somebody who prays the Amida even beyond four Amot, if the person praying can see him, Hacham Ovadia Yosef disagrees. Hacham Ovadia maintains that one may follow the view of the Shulhan Aruch and pass in front of somebody praying the Amida if he is beyond four Amot of the person.
It should be noted that this Halacha applies only to passing in front of a person praying the Amida. It is permissible to step back if he will then be positioned to the side of somebody praying the Amida, since he will not be in front of him.
If a Hazan has completed the Amida and wishes to begin the repetition, but somebody is praying the Amida right behind him, thus preventing him from stepping back, then he should begin the repetition without stepping back for "Oseh Shalom." This is the ruling of Hacham Ovadia Yosef. Hacham Ovadia writes that in such a case, the Hazan may rely on the three steps back he will take for "Oseh Shalom" at the end of "Kaddish Titkabal" later in the prayer service.
It is customary for the Hazan to wait before beginning the repetition of the Amida until the Hacham in the synagogue has completed the Amida. If the Hacham has completed the Amida but somebody is praying the Amida right behind, thus preventing him from stepping back and reciting "Oseh Shalom," then the Hacham may signal with his hand to the Hazan that he may begin the repetition. Rather than delay the prayer service, it is permissible for the Hacham to silently gesture to the Hazan so he can proceed with the repetition of the Amida.
Summary: One may not take three steps back for "Oseh Shalom" upon completing the Amida if he will then be within four Amot of somebody praying behind him. A Hazan in this situation may begin the repetition of the Amida without stepping back for "Oseh Shalom." If a Rabbi is in this situation and the congregation is waiting for him to finish the Amida before beginning the Hazan’s repetition, he may silently gesture to the Hazan to proceed with the repetition.
