Sahih Bukhari Volume 008, Book 073, Hadith Number 053.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 73. Good Manners and Form (Al-Adab)
Narated By 'Aisha : (The wife of the Prophet) A group of Jews entered upon the Prophet and said, "As-Samu-Alaikum." (i.e. death be upon you). I understood it and said, "Wa-Alaikum As-Samu wal-la'n. (death and the curse of Allah be Upon you)." Allah's Apostle said "Be calm, O 'Aisha! Allah loves that on, should be kind and lenient in all matters." I said, "O Allah's Apostle! Haven't you heard what they (the Jews) have said?" Allah's Apostle said "I have (already) said (to them) "And upon you!"