He, sallallaahu ‘alayhi wa sallam, used to train them to use good words and refrain from ill speech:

‘Aa’ishah narrated that some Jews came to the Prophet of Allah, sallallaahu ‘alayhi wa sallam, and said: “As-Saamu ‘Alaykum” (which means, death be on you). The Prophet of Allah, sallallaahu ‘alayhi wa sallam, and said: “Wa ‘Alaykum” (which means, and on you too). ‘Aa’ishah said (to them), “Death be on you, and may Allah curse you and shower His wrath upon you!” The Prophet of Allah, sallallaahu ‘alayhi wa sallam, said: “Be calm, O ‘Aa’ishah! You should be kind and lenient, and beware of roughness and bad words.” She said (to the Prophet), “Haven’t you heard what they (Jews) have said?” He, sallallaahu ‘alayhi wa sallam, said: “Haven’t you heard what I have said [to them]? I said the same to them, and my invocation against them will be accepted while theirs against me will be rejected [by Allah].”