It is better to say, "And upon you be peace and the mercy of Allah," when he says, "Peace be upon you." And to add, "and His blessings," when he says, "and the mercy of Allah." It has been narrated that a man said to the Messenger of Allah, blessings and peace be upon him: "Peace be upon you." He said, "And upon you be peace and the mercy of Allah." Another said: "Peace be upon you and the mercy of Allah." He said, "And upon you be peace and the mercy of Allah and His blessings." Another said: "Peace be upon you and the mercy of Allah and His blessings." He said, "And upon you." [Narrated by al-Tabarani and al-Tabari from the narration of Hisham ibn Aasim al-Ahwal from Abu Othman from Salman. Ibn al-Jawzi said in al-'Ilal: He abandoned the hadith of Hisham. Al-Tabarani also narrated it from the narration of Ikrimah from Ibn Abbas. The narrator from Ikrimah is Abu Hurairah from Nafi' from Harmuz. And he is weak.] The man said: "You have diminished me, so where is what Allah said?" And he recited the verse. He said: "You have not left me with a favor, so I returned to you something like it. Or respond to it or answer it with something like it." The response to the greeting and its return is to respond to it with something similar, because the responder repeats the words of the Muslim. The response to the greeting is obligatory, and the choice is only between adding to it or leaving it. And from Abu Yusuf, may Allah have mercy on him: If someone says to another: "Convey my greetings to so-and-so," it is obligatory upon him to do so. And from al-Nakha'i: The greeting is a Sunnah and the response is an obligation. And from Ibn Abbas: The response is mandatory. There is no man who passes by a group of Muslims and greets them, and they do not respond to him, except that the spirit of holiness is taken away from them, and the angels respond to him. And the greeting is not to be returned during the sermon, the recitation of the Qur'an, loudly narrating hadith, during the study of knowledge, the call to prayer, and the establishment of the prayer. And from Abu Yusuf: One should not greet a player of dice or chess, a singer, someone sitting for a need, a pigeon keeper, or someone naked without excuse in a bath or elsewhere. And al-Tahawi mentioned: It is recommended to respond to the greeting while in a state of purity. And it is reported from the Prophet, blessings and peace be upon him, that he performed tayammum to respond to the greeting. [Narrated by al-Bukhari from the narration of 'Amir, the freed slave of Ibn Abbas, who said: "I and Abdullah ibn Yasar, the freed slave of Maimunah, the wife of the Prophet, blessings and peace be upon him, entered upon Abu al-Jahm ibn al-Harith ibn al-Simmah al-Ansari. Abu al-Jahm said: The Messenger of Allah, blessings and peace be upon him, came from the direction of the Well of Jamal, and a man met him and greeted him, but he did not respond to him until he reached the wall, then he wiped his face and hands and then responded to the greeting." And Muslim narrated it as a commentary. And from Abu Dawood from Ibn 'Amir: "A man passed by the Messenger of Allah, blessings and peace be upon him, in a street, having just come out from relieving himself. He greeted him, but he did not respond to him until the man was about to disappear in the street. He struck his hand on the wall and wiped his face, then struck another blow and wiped his arms, then responded to the greeting, saying: 'Nothing prevented me from responding to your greeting except that I was not in a state of purity.' "] They said: A man should greet when he enters upon his wife, and he should not greet a non-mahram woman. The walker greets the one sitting, the rider greets the walker, the rider of the horse greets the rider of the donkey, the small greets the large, and the lesser greets the greater. And when they meet, they should initiate the greeting. And from Abu Hanifah: Do not raise your voice in response, meaning excessive loudness. And from the Prophet, blessings and peace be upon him: "When the People of the Book greet you, say: 'And upon you.'" [Agreed upon from the hadith of Anas, may Allah be pleased with him.] This means: 'And upon you what you said,' because they used to say: 'Death be upon you.' It is narrated: "Do not initiate the greeting with a Jew, but if he greets you, say: 'And upon you.'" And from al-Hasan: It is permissible to say to a disbeliever: 'And upon you be peace,' but do not say: 'and the mercy of Allah,' for it is a supplication for forgiveness. And from al-Shabi, he said to a Christian who greeted him: 'And upon you be peace and the mercy of Allah.' He was asked about this, and he said: 'Isn't it by the mercy of Allah that he lives?' Some scholars have permitted the People of the Covenant to initiate the greeting if a situation arises that necessitates it.

And this was narrated from Al-Nakha'i. And from Abu Hanifa: Do not begin with peace in writing or otherwise. And from Abu Yusuf: Do not greet them with peace nor shake hands with them. And when you enter, say: Peace be upon those who follow guidance. And there is no harm in supplicating for him with what will rectify him in his worldly affairs. Indeed, He is All-Aware of everything, meaning He will hold you accountable for everything, including greetings and others.