Arabic (Original)
حَدَّثَنَا سُفْيَانُ سَمِعْتُهُ مِنِ ابْنِ دِينَارٍ عَنِ ابْنِ عُمَرَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا سَلَّمَ عَلَيْكَ الْيَهُودِيُّ فَإِنَّمَا يَقُولُ السَّامُ عَلَيْكَ فَقُلْ وَعَلَيْكَ وَقَالَ مَرَّةً إِذَا سَلَّمَ عَلَيْكُمْ الْيَهُودُ فَقُولُوا وَعَلَيْكُمْ فَإِنَّهُمْ يَقُولُونَ السَّامُ عَلَيْكُمْ.
English Translation
Sufyan narrated to us - I heard it from Ibn Dinar - from Ibn 'Umar, from the Prophet, peace and blessings be upon him: "When a Jew greets you with salam, he only says 'as-Sam 'alayka' (death be upon you), so say 'wa 'alayka' (and upon you)." And he said another time: "When the Jews greet you with salam, say 'wa 'alaykum' (and upon you), for they say 'as-Samu 'alaykum'."