When the Jews offer you salutations, some of them say as-Sam-u-'Alaikum (death be upon you). You should say (in response to it): Let it be upon you.  

قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْيَهُودَ إِذَا سَلَّمُوا عَلَيْكُمْ يَقُولُ أَحَدُهُمُ السَّامُ عَلَيْكُمْ فَقُلْ عَلَيْكَ  

The Prophet ﷺ said: When one of the Jews greets you saying: Death may come upon you, reply: The same to you. Abu Dawud said: Malik b. 'Adb Allah b. Dinar transmitted it in a similar manner, and al-Thawri transmitted it from 'Abd Allah b. Dinar. He said in this version: The same to you.  

أَنَّهُ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْيَهُودَ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدُهُمْ فَإِنَّمَا يَقُولُ السَّامُ عَلَيْكُمْ فَقُولُوا وَعَلَيْكُمْ  

That the Messenger of Allah ﷺ said: "Indeed when a Jew gives Salam to one of you, then he is only saying: 'As-Samu 'Alaikum' (Death be upon you) so say: "Alaik (And upon you).'"  

قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْيَهُودَ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدُهُمْ فَإِنَّمَا يَقُولُ السَّامُ عَلَيْكُمْ فَقُلْ عَلَيْكَ  

Yahya related to me from Malik from Abdullah ibn Dinar that Abdullah ibn Umar said that the Messenger of Allah ﷺ said, "When a jew greets you, and says 'Death to you' (as-samu alaykum) say, 'And to you.' " Yahya said, "Malik was asked whether a person who greeted a jew or christian, should apologise for it. He said, 'No'."  

أَنَّهُ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْيَهُودَ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدُهُمْ فَإِنَّمَا يَقُولُ السَّامُ عَلَيْكُمْ فَقُلْ عَلَيْكَ۔ وسُئِلَ مالِكٌ عَمَّنْ سَلَّمَ عَلى اليَهُودِيِّ أوِ النَّصْرانِيِّ هَلْ يَسْتَقِيلُهُ ذلِكَ؟ فَقالَ: لاَ  

[Machine] I heard Anas say that a man from the people of the Book came and greeted the Prophet ﷺ . He said "As-Salamu Alaykum" (peace be upon you), and Umar said, "O Messenger of Allah, should I not strike his neck?" The Prophet ﷺ said, "No, if they greet you with peace, then say 'wa 'alaykum" (and peace be upon you too).  

سَمِعْتُ أَنَسًا يَقُولُ جَاءَ رَجُلٌ مِنْ أَهْلِ الْكِتَابِ فَسَلَّمَ عَلَى النَّبِيِّ ﷺ فَقَالَ السَّامُ عَلَيْكُمْ فَقَالَ عُمَرُ يَا رَسُولَ اللهِ أَلَا أَضْرِبُ عُنُقَهُ؟ قَالَ لَا إِذَا سَلَّمُوا عَلَيْكُمْ فَقُولُوا وَعَلَيْكُمْ  

[Machine] Indeed, the Prophet ﷺ said, "Verily, when the Jews greet you, they say 'as-salamu 'alaykum' (peace be upon you).’ Therefore, the Prophet ﷺ said to respond by saying 'wa 'alayka' (and upon you)’."  

أَنَّ النَّبِيَّ ﷺ قَالَ إِنَّ الْيَهُودَ إِذَا سَلَّمُوا عَلَيْكُمْ قَالُوا السَّامُ عَلَيْكُمْ فَقَالَ النَّبِيُّ ﷺ فَقُلْ وَعَلَيْكَ