There is no objection to commencing with "salam" to them, but it is discouraged (makruh) except when necessary, even if it is customary. Their "salam" should be replied by saying "'alayk." There is no objection to congratulating them on special occasions. (MMS, pp. 31-32, Q63)
http://www.najaf.org…2/inside/65.html
We are instructed by the Ahl Al-Bayt (as) to respond to their salaams with عَلَيْكُمْ "`alaykum" or وَ عَلَيْكُمْ "wa `alaykum"
لَا تَبْدَءُوا أَهْلَ الْكِتَابِ بِالتَّسْلِيمِ وَ إِذَا سَلَّمُوا عَلَيْكُمْ فَقُولُوا وَ عَلَيْكُمْ
‘Do not initiate salaam (with) the Ahl Al-Kitaab (People of the book) , but if they offered salaam onto you, just say, “wa ‘Alaykum”’
• Source:
• Al-Kulayni, Al-Kaafi, vol. 2, pg. 648 – 649, hadeeth # 2
• Grading:
• Al-Majlisi said this hadeeth is Muwaththaq (Reliable)
• –> Mir'aat Al-`Uqool, vol. 12, pg. 546
سَأَلْتُ أَبَا عَبْدِ اللَّهِ ع عَنِ الْيَهُودِيِّ وَ النَّصْرَانِيِّ وَ الْمُشْرِكِ إِذَا سَلَّمُوا عَلَى الرَّجُلِ وَ هُوَ جَالِسٌ كَيْفَ يَنْبَغِي أَنْ يَرُدَّ عَلَيْهِمْ فَقَالَ يَقُولُ عَلَيْكُمْ
“I asked Aboo `Abd Allaah (as), about Jewish, Christians and the Mushrik greetings to one sitting, how should he respond onto them? So he (as) said,‘He will say, ‘‘Alaykum’”
• Source:
• Al-Kulayni, Al-Kaafi, vol. 2, pg. 649, hadeeth # 3
• Grading:
• Al-Majlisi said this hadeeth is Muwaththaq (Reliable)
• –> Mir'aat Al-`Uqool, vol. 12, pg. 546
إِذَا سَلَّمَ عَلَيْكَ الْيَهُودِيُّ وَ النَّصْرَانِيُّ وَ الْمُشْرِكُ فَقُلْ عَلَيْكَ
"If a Jew, Christain or a Mushrik says salaam to you, he (should) say: `Alayk
• Source:
• Al-Kulayni, Al-Kaafi, vol. 2, pg. 649, hadeeth # 4
• Grading:
• Al-Majlisi said this hadeeth is Muwaththaq (Reliable)
• –> Mir'aat Al-`Uqool, vol. 12, pg. 546
قُلْتُ لِأَبِي الْحَسَنِ مُوسَى ع أَ رَأَيْتَ إِنِ احْتَجْتُ إِلَى الطَّبِيبِ وَ هُوَ نَصْرَانِيٌّ أَنْ أُسَلِّمَ عَلَيْهِ وَ أَدْعُوَ لَهُ قَالَ نَعَمْ إِنَّهُ لَا يَنْفَعُهُ دُعَاؤُكَ
I asked Aboo Al-Hasan Moosa (as) ‘If I needed to visit a physician and he is a Christain, can I offer salaam and pray for him?’ He (as) said:, ‘Yes, but your prayer will not benefit him.’”
• Source:
• Al-Kulayni, Al-Kaafi, vol. 2, pg. 650, hadeeth # 7
• Grading:
• Al-Majlisi said this hadeeth is Hasan (Good)
• –> Mir'aat Al-`Uqool, vol. 12, pg. 547