Answered by Shaykh Faraz Rabbani
If two people give salams at the same time, do both have to repeat their salams? Or?
Walaikum assalam wa rahmatullah,
I pray that this finds you well, and in the best of health and spirits. May Allah grant you all good and success in this life and the next.
If two people greet each other at the same time, then each person’s salams are also considered–effectively–to be a reply to the other’s salams, and neither has to make a subsequent reply. [Abu’l Su`ud, Fath al-Mu`in `ala Sharh Mulla Miskin `ala Kanz al-Daqa’iq]
However, it would be superior to give the reply, anyways, to avoid the difference of opinion of the Shafiis (and others) who hold that the reply would remain necessary. [Nawawi, al-Adhkar]
And Allah alone gives success.
Faraz Rabbani