'Abdullah ibn 'Umar said that the Messenger of Allah, may Allah bless him and grant him peace, said, "When one of the Jews greets you and says, 'Poison be upon you (as-samu 'alaykum),' say, 'And on you.'"  

قَالَ رَسُولُ اللهِ ﷺ إِنَّ الْيَهُودَ إِذَا سَلَّمَ عَلَيْكُمْ أَحَدُهُمْ فَإِنَّمَا يَقُولُ السَّامُ عَلَيْكَ فَقُولُوا وَعَلَيْكَ  

Ibn 'Abbas said, "Return the greeting to whomever it is, Jew, Christian, or Magian. That is because Allah says, 'When you are greeted with a greeting, greet with one better than it or return it.' (4:86)"  

بِأَنَّ اللَّهَ يَقُولُ {وَإِذَا حُيِّيتُمْ بِتَحِيَّةٍ فَحَيُّوا بِأَحْسَنَ مِنْهَا أَوْ رُدُّوهَا}