A Jew came to the Prophet of Allah and his Companions and said: “As-Samu Alaikum (Death be upon you).” So the people replied to him. The Prophet of Allah said: “Do you know what this person said?” They said: “Allah and His Messenger know better – he said the Salam – O Allah’s Prophet.” He said: “No, rather he said like this and that. Bring him back for e=me.” So they brought him back and he said: “Did you say As-Samu Alaikum? He said: “Yes.” So with that Allah’s Prophet said: “When one of the People of the Book gives you the Salam, then say: “Alaika Ma Qulta (Whatever you said to you too).” He said: ‘And when they come to you, they greet you with a greeting wherewith Allah greets you not.’ (Using translation from Tirmidhī 3301)   

أَنَّ يَهُودِيًّا مَرَّ عَلَى رَسُولِ اللهِ ﷺ وَأَصْحَابِهِ فَقَالَ السَّامُ عَلَيْكُمْ فَقَالَ نَبِيُّ اللهِ ﷺ أَتَدْرُونَ مَا قَالَ هَذَا؟ قَالُوا سَلَّمَ يَا رَسُولَ اللهِ قَالَ لَا وَلَكِنَّهُ قَالَ كَذَا وَكَذَا ثُمَّ قَالَ رُدُّوهُ عَلَيَّ فَرَدُّوهُ عَلَيْهِ فَقَالَ قُلْتَ السَّامُ عَلَيْكُمْ قَالَ نَعَمْ فَقَالَ نَبِيُّ اللهِ ﷺ عِنْدَ ذَلِكَ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدٌ مِنْ أَهْلِ الْكِتَابِ فَقُولُوا وَعَلَيْكَ أَيْ وَعَلَيْكَ مَا قُلْتَ  

[Machine] A Jew came to the Prophet ﷺ while he was with his companions, and he said, "Peace be upon you." The people replied to him and said, "And upon you be peace, O Messenger of Allah." The Prophet ﷺ then asked them, "Do you know what he said?" They said, "Yes, he said, 'Peace be upon you.'" The Prophet ﷺ said, "Respond to him by saying, 'Upon you be the same.'" So they responded to the man and said, "Upon you be the same." Then the Prophet ﷺ asked the man, "Did you say such and such?" He said, "Yes." The Prophet ﷺ then said, "When anyone from the People of the Book greets you with peace, say, 'And upon you be peace,' meaning upon you be what you have said."  

أَنَّ يَهُودِيًّا أَتَى النَّبِيَّ ﷺ وَهُوَ مَعَ أَصْحَابِهِ فَقَالَ السَّامُ عَلَيْكُمْ فَرَدَّ عَلَيْهِ الْقَوْمُ فَقَالَ نَبِيُّ اللهِ ﷺ أَتَدْرُونَ مَا قَالَ؟ قَالُوا نَعَمْ قَالَ السَّامُ عَلَيْكُمْ قَالَ رُدُّوا عَلَيَّ الرَّجُلَ فَرَدُّوهُ فَقَالَ نَبِيُّ اللهِ ﷺ قُلْتَ كَذَا وَكَذَا؟ قَالَ نَعَمْ فَقَالَ نَبِيُّ اللهِ ﷺ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدٌ مِنْ أَهْلِ الْكِتَابِ فَقُولُوا عَلَيْكَ أَيْ عَلَيْكَ مَا قُلْتَ