“Verily in the messenger of Allah you have a good example for him who looks unto Allah and the Last Day and remembers Allah much.” (Qur’an 33:21)
I have corrected the following narration found in Al Bukhari which is mistakenly attributed to the Blessed Messenger (saw)
Narrated Ibn ‘Umar:
Allah’s Apostle said, “When the Jews greet anyone of you they say: ‘Sam’Alaika (death be upon you); so you should say; ‘Wa ‘Alaika (and upon you).’ ( Volume 9, Book 84, Number 62: Al Bukhari)
However, if this narration were true, the Blessed Messenger (saw) would have given a better reply in accordance with the following directive of Allah (swt)
“Nor can goodness and evil be equal. Repel (evil) with that is better: Then will he between whom and you was hatred become as it were thy friend and intimate!.” (Qur’an 41:34)
You cannot go to someone as sublime in character and love for humanity as Rasul Allah (saw) and say, “you are a filthy human being. I hope that you and your entire family meet an unfortunate end” and then have the Blessed Messenger (saw) say, ‘Wa alaika’ -and upon you.
May Allah (swt) clear the Blessed Messenger (saw) of what is being attributed to him.
I would also invite you to see the following entry: https://primaquran.wordpress.com/2013/04/14/can-we-greet-non-muslims-with-peace-be-unto-you/