Sahih Bukhari

Narrated `Aisha:The Jews used to greet the Prophet (ﷺ) by saying, ""As-Samu 'Alaika (i.e., death be upon you), so I understood what they said, and I said to them, ""As-Samu 'alaikum wal-la'na (i.e. Death and Allah's Curse be upon you)."" The Prophet (ﷺ) said, ""Be gentle and calm, O `Aisha, as Allah likes gentleness in all affairs."" I said, ""O Allah's Prophet! Didn't you hear what they said?"" He said, ""Didn't you hear me answering them back by saying, 'Alaikum (i.e., the same be upon you)?