When concluding the prayer with "Peace be upon you and the mercy of Allah," to whom is this salutation directed?

The meaning of the tasleem (salutation) in prayer is to exit from it. The worshiper, by his tasleem, intends to greet those to his right and left, the angels, and the Muslim jinn.

Ahmad stipulated that there is no harm in intending thereby to return the greeting to the two angels (recording deeds) and to those behind him if he is an imam (prayer leader), or to the imam and those with him if he is a ma'mum (follower).

Abu Hafs held the view that the first tasleem is for exiting the prayer, and the second is for greeting the guardian angels and the followers if he is an imam, and for returning the greeting to the imam and the guardian angels if he is a ma'mum.

The Shafi'is differentiate between the imam, the ma'mum, and the munfarid (one praying alone) in the intention of the tasleem.