557. Performing Mitzvos for Others

Brachos 11:13

If one affixes a mezuzah for another person, he recites a bracha that God commanded us “regarding the affixing of a mezuzah.” If he installs a guardrail for another person, he recites “regarding the installation of a guardrail.” If he separates terumah for another person, he recites “regarding the separation of terumah.” If he circumcises another person’s son, he recites “regarding circumcision.” The same is true in all such situations.

Brachos 11:14

When one performs a mitzvah for both himself and others, then if the mitzvah is not obligatory, he recites that God “commanded us regarding” the mitzvah, such as “regarding the mitzvah of eiruv.” If the mitzvah is obligatory and he intended to fulfill both his own obligation and that of others, he recites that God “commanded us to…,” such as “to hear the sound of the shofar.”