It is recommended that the one who initiates the greeting say: "Peace be upon you, and the mercy of Allah and His blessings." He uses the plural pronoun, even if the one being greeted is a single person. The one who responds says: "And upon you be peace, and the mercy of Allah and His blessings," bringing in the conjunctive wāw in his words: "And upon you."
Hadith850
﵄، - ﷺ - ﷺ:
On the authority of ʿImrān ibn al-Ḥuṣayn (may Allah be pleased with them both), who said: A man came to the Prophet (peace and blessings be upon him) and said: "Peace be upon you." He returned the greeting to him, then [the man] sat down, and the Prophet (peace and blessings be upon him) said: "Ten." Then another came and said: "Peace be upon you, and the mercy of Allah." He returned the greeting to him, and [the man] sat down, and he said: "Twenty." Then another came and said: "Peace be upon you, and the mercy of Allah and His blessings." He returned the greeting to him, and [the man] sat down, and he said: "Thirty." Narrated by Abū Dāwūd and al-Tirmidhī, who said: "A good ḥadīth."
Hadith851
﵂، - ﷺ: .
On the authority of ʿĀʾishah (may Allah be pleased with her), who said: The Messenger of Allah (peace and blessings be upon him) said to me: "This is Gabriel, conveying greetings of peace to you." She said: I replied: "And upon him be peace, and the mercy of Allah and His blessings." Agreed upon. Thus it occurs in some narrations of the two Ṣaḥīḥs with "and His blessings," and in some of them it is omitted; and the addition by a trustworthy narrator is accepted.
On the authority of Anas (may Allah be pleased with him): that the Prophet (peace and blessings be upon him), when he spoke a word, would repeat it three times until it was understood from him; and when he came upon a group and greeted them, he would greet them three times. Narrated by al-Bukhārī. This is understood to refer to when the gathering was large.
On the authority of al-Miqdād (may Allah be pleased with him), in his lengthy ḥadīth, who said: We used to set aside for the Prophet (peace and blessings be upon him) his share of the milk, and he would come during the night and give a greeting that would not wake one who was asleep yet would be heard by one who was awake. The Prophet (peace and blessings be upon him) came and greeted just as he used to greet. Narrated by Muslim.
On the authority of Asmāʾ bint Yazīd (may Allah be pleased with her): that the Messenger of Allah (peace and blessings be upon him) passed through the mosque one day, while a group of women were sitting, and he gestured with his hand in greeting. Narrated by al-Tirmidhī, who said: "A good ḥadīth." This is understood to mean that he (peace and blessings be upon him) combined the spoken word with the gesture; this is supported by the fact that in Abū Dāwūd's narration it states: "He greeted us."
On the authority of Abū Umāmah (may Allah be pleased with him), who said: The Messenger of Allah (peace and blessings be upon him) said: "The closest of people to Allah are those who are first to greet them with the salām." Narrated by Abū Dāwūd with a good chain, and al-Tirmidhī also narrated it in similar wording and said: "A good ḥadīth." And it has already been mentioned after this. [review: terse editorial note وقد ذُكر بعده — rendered literally]
On the authority of Abū Jurayy al-Hujaymī (may Allah be pleased with him), who said: I came to the Messenger of Allah (peace and blessings be upon him) and said: "Upon you be peace, O Messenger of Allah." He said: "Do not say 'Upon you be peace,' for 'Upon you be peace' is the greeting of the dead." Narrated by Abū Dāwūd and al-Tirmidhī, who said: "A good and sound ḥadīth." And it has already been mentioned in full.