✅ Answer: Pay attention to the following hadiths (traditions):

1 عَنْ عَلِیِّ بْنِ إِبْرَاهِیمَ عَنْ أَبِیهِ عَنِ النَّوْفَلِیِّ عَنِ السَّکُونِیِّ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ: قَالَ رَسُولُ اللَّهِ السَّلَامُ تَطَوُّعٌ وَ الرَّدُّ فَرِیضَةٌ.

📚 Al-Kafi Vol. 2, p. 644

Imam Sadiq (peace be upon him) said: The Messenger of Allah (peace and blessings be upon him and his family) said: Giving a greeting (Salam) is voluntary (Tattavvu' and Mustahabb), and returning a greeting is an obligation (Faridha)!

2 عَنْ عِدَّةٍ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِیَادٍ عَنْ عَلِیِّ بْنِ أَسْبَاطٍ عَنِ ابْنِ بُکَیْرٍ عَنْ بَعْضِ أَصْحَابِهِ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ إِذَا مَرَّتِ الْجَمَاعَةُ بِقَوْمٍ أَجْزَأَهُمْ أَنْ یُسَلِّمَ وَاحِدٌ مِنْهُمْ وَ إِذَا سَلَّمَ عَلَی الْقَوْمِ وَ هُمْ جَمَاعَةٌ أَجْزَأَهُمْ أَنْ یَرُدَّ وَاحِدٌ مِنْهُمْ.

📚 Al-Kafi Vol. 2, p. 647

Imam Sadiq (peace be upon him) said: When a group passes by a congregation, it is sufficient for one of them to give the greeting, and if an individual passes by a people who are a congregation, it is sufficient for one of them to return the greeting!

3 عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ مُحَمَّدِ بْنِ یَحْیَی عَنْ غِیَاثِ بْنِ إِبْرَاهِیمَ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ: إِذَا سَلَّمَ مِنَ الْقَوْمِ وَاحِدٌ أَجْزَأَ عَنْهُمْ وَ إِذَا رَدَّ وَاحِدٌ أَجْزَأَ عَنْهُمْ.

📚 Al-Kafi Vol. 2, p. 647

Imam Sadiq (peace be upon him) said: When one person from a group gives the greeting, it suffices for all of them, and if one person returns the greeting, it suffices for all of them!

✅ Based on the above hadiths, returning a greeting is an obligation, but if an individual greets a congregation, if one of that congregation returns the greeting, it suffices for all of them, and it is not necessary for all of them to return the greeting individually.

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْر

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