In the previous Halachot we have explained that one may not stand or pass in front of one praying Amida.
Let us now discuss the law regarding one who has concluded his Amida prayer and behind him stands another congregant who has not yet concluded his Amida. If, at this point, the individual in front were to take the customary three steps back marking the conclusion of the Amida, he will thereby be entering the four Amot of another individual who is praying.
Thus, if one concludes his Amida prayer and realizes that the person behind him is still praying, one may not take three steps back; rather, one must stand in place until the individual behind him concludes his Amida prayer. The same applies to women, especially during the High Holidays when the Amida prayers are longer than usual and one woman finishes praying while another woman behind her has not yet concluded her prayer; the woman in front may not take three steps back until the woman behind her takes her customary three steps back.
As we have discussed, this prohibition applies only when one enters the four Amot (6.5 feet) and when one will be standing directly in front of the one praying. However, if one does not enter the four Amot of the one praying behind him or if one is not standing directly in front of him and is on his side, one may take his customary three steps back and recite “Osseh Shalom.”
The Law Regarding a Chazzan
If a Chazzan concludes his silent Amida prayer but cannot take three steps back because there is a congregant still praying behind him but cannot wait since doing so will mean delaying the entire congregation, the Chazzan should not take three steps back; rather, he should immediately begin the repetition of the Amida and at the conclusion of the repetition, he should recite “Osseh Shalom” in an undertone and then take three steps back. If the Chazzan decides to take three steps back at the conclusion of his silent Amida and not to wait, he indeed has on whom to rely.
Summary: If one concludes one Amida prayer and there is another individual still praying behind him, one may not take three steps back until the person behind him concludes his prayer, for one cannot stand directly in front of one praying within four Amot. If the individual still praying is not directly behind him or if he is more than four Amot away (and even after taking three steps back, one will not enter his four Amot), one may take three steps back immediately.