And it is astonishing that al-Nawawī, after explicitly declaring in al-Adhkār that greeting a person who is praying is disliked, then went on to say:
“Rather, what is recommended is that he return the salām during the prayer by means of a gesture, without uttering anything.”
I say: The reason for this astonishment is that deeming the response recommended necessarily entails that offering the greeting in the first place is likewise recommended—and the converse is equally true—because the proof for both rulings is one and the same: this ḥadith and others of similar purport. If it establishes the recommendation of returning the greeting, it simultaneously establishes the recommendation of initiating it. Had the latter been disliked, the Messenger of Allah ﷺ would have made that clear—even if only by not responding with a gesture—since it is a firmly established principle that delaying clarification beyond the time of need is impermissible. This is obvious and manifest; praise belongs to Allah.
The same applies to greeting the muʾadhdhin and the one reciting the Quran: it is legislated, and the proof is what has preceded. For once greeting the person who is praying is deemed recommended, greeting the muʾadhdhin and the reciter is even more appropriate. I recall having read in the Musnad a ḥadith in which the Prophet ﷺ greeted a group who were reciting the Quran, and I had hoped to cite it here and discuss its chain of transmission, but I have not been able to locate it at present.
As for whether they should return the greeting verbally or merely by gesture, the apparent view is the first. Al-Nawawī said: “As for the muʾadhdhin, it is not disliked for him to respond in his customary wording, for that is brief and neither invalidates nor compromises the adhān.”
Among the matters derived from this is repeating the salām after a separation—even a brief one—because of his ﷺ statement:
“When one of you meets his brother, let him greet him with salām. If a tree, wall, or stone comes between them and he meets him again, let him greet him with salām once more.”
186 – “When one of you meets his brother, let him greet him with salām. If a tree, wall, or stone comes between them and he meets him again, let him greet him with salām once more.”
It was narrated by Abū Dāwūd (5200) via the route of Ibn Wahb, who said: “Maʿwiyah ibn Ṣāliḥ informed me, from Abū Mūsā, from Abū Maryam, from Abū Hurayrah, who said: ‘When …’” Maʿwiyah added: “And he also narrated to me …”