Greeting a person offering Salah

A: Firstly, it is prescribed for a Muslim to initiate the greeting of Salam to his Muslim brothers during their Salah, but they should not return the Salam whilst praying, except by making a gesture in a manner that will maintain the validity of their Salah. It is narrated on the authority of Ibn `Umar (may Allah be pleased with them) that he said, I asked Bilal, how did the Messenger of Allah (peace be upon him) return their Salam when they greeted him whilst he was performing Salah? He said, 'With a gesture of his hand.' (Part No. 7; Page No. 32)  Narrated by the Five Compilers of Hadith (Imams Ahmad, Abu Dawud, Al-Tirmidhy, Al-Nasa'y and Ibn Majah). It is also narrated from him on the authority of Suhayb (may Allah be pleased with them) who said, I passed by the Messenger of Allah (peace be upon him) while he was praying. I saluted him and he returned it by making a sign. The narrator said: I do not know but that he said: He made a sign with his finger. Narrated by the Five Compilers of Hadith (Imams Ahmad, Abu Dawud, Al-Tirmidhy, Al-Nasa'y and Ibn Majah) apart from Ibn Majah. Al-Tirmidhy said, "Both Hadith are authentic in my view." It is also authentically reported on the authority of Um Salamah (may Allah be pleased with her) that she said, I heard the Prophet (peace be upon him) forbidding us to pray two Rak`ahs after `Asr (Afternoon) Prayer, then I saw him praying them when he performed `Asr (Afternoon) Prayer. She said, he entered and there were some women from Banu Haram, a clan of Al-Ansar, with me. He started to pray them, these two Rak`ahs after `Asr (Afternoon) Prayer, so I sent a young girl to him, and told her, "Stand beside him and say to him, Um Salamah is saying to you, O Messenger of Allah, I heard you forbidding us to do these two Rak`ahs and now I see you praying them. If he makes a gesture with his hand then leave him and go back." So the young girl did that and he made a gesture with his hand, so she left him and went back. When he finished performing his Salah, he said, "O daughter of Abu Umayyah, you asked about the two Rak`ahs after `Asr (Afternoon) Prayer. Some people from Banu `Abdul-Qays came to me and kept me from doing the two Rak`ahs after Zhuhr (Noon) Prayer and it is those two Rak`ahs you saw me observing. Narrated by Al-Bukhari (Part No. 7; Page No. 33) and Muslim. These Hadith indicate that it is prescribed to say Salam to a person during Salah and he should respond to the greeting with a gesture, because this is what the Prophet (peace be upon him) approved, of initiating the Salam, and returning it with a gesture only [when in Salah]. Secondly, it is prescribed for a Muslim to initiate a greeting to a person who is engaged in performing Dhikr (Remembrance of Allah) or Du`a' (supplication), because it was authentically reported on the authority of Abu Waqid Al-Laythy (may Allah be pleased with him), that he said, Whilst the Prophet (peace be upon him) was sitting in the Masjid (mosque) with some people, three people came in; two of them came to the Messenger of Allah (peace be upon him) and one went away. When they came up to the Messenger of Allah (peace be upon him), they greeted him with Salam. One of them found a space in the circle and sat down. The other sat down behind him. The third one turned and went away. When the Messenger (peace be upon him) finished (his talk), he said: "Shall I tell you about the three people? One of them turned to Allah, so Allah accepted him; the second felt shy so Allah will feel shy (to punish him); and the third turned away, so Allah turned away from him." And what is narrated in the two Sahih on the authority of Abu Hurayrah (may Allah be pleased with him) that A Bedouin entered the Masjid and offered Salah, but he did not do the Ruku` (bowing) and Sujud (Prostration) properly. Then, he came and greeted the Prophet (peace be upon him) with Salam. The Prophet (peace be upon him) returned his greeting then said, "Go back and pray, for you have not prayed." (Part No. 7; Page No. 34) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.