Evil should not be uttered in public

Allah does not like that the evil should be uttered in public except by him who has been wronged. And Allah is Ever All-Hearer, All-Knower. 

[Qur'aan 4:148]

فقال بعضهم : معنى ذلك : لا يحب الله - تعالى ذكره - أن يجهر أحدنا بالدعاء على أحد ، وذلك عندهم هو " الجهر بالسوء إلا من ظلم" 

A group of scholars said that the meaning of that is that Allah does not like that anyone of us makes duaa' (supplication) against anyone. And that is the meaning, in their opinion, of the portion which reads "evil should not be uttered in public except by him who has been wronged."

يقول : إلا من ظلم فيدعو على ظالمه ، فإن الله جل ثناؤه لا يكره له ذلك ، لأنه قد رخص له في ذلك

They say the exception is the one who has been wronged. He has the right to make supplication against the person who wronged him. Allah does not dislike that because he has given him dispensation regarding that.

They were cursed

لُعِنَ الَّذِينَ كَفَرُوا مِن بَنِي إِسْرَائِيلَ عَلَىٰ لِسَانِ دَاوُودَ وَعِيسَى ابْنِ مَرْيَمَ ۚ ذَٰلِكَ بِمَا عَصَوا وَّكَانُوا يَعْتَدُونَ

Cursed were those who disbelieved among the Children of Israel by the tongue of David and of Jesus, the son of Mary. That was because they disobeyed and [habitually] transgressed.

[Qur'aan 5:78]

قال أبو جعفر: يقول تعالى ذكره لنبيه محمد صلى الله عليه وسلم

'Abu Ja'far said: He said to His Prophet (sallallaahu 'alayhi wa sallam)

قل لهؤلاء النصارى الذين وصفَ تعالى ذكره صفتهم

Say to these Christians who characterized [Allah] with their characterization 

لا تغلوا فتقولوا في المسيح غير الحق

Do not transgress and consequently say regrading The Maseeh [i.e. Jesus] that which is not true

ولا تقولوا فيه ما قالت اليهود الذين قد لعنهم الله على لسان أنبيائه ورسله، داود وعيسى ابن مريم

And do not say regarding him that which the Jews who Allah cursed by the tongue of His Prophets and Messengers - Daawud and Jesus the son of Marry - said

حدثني محمد بن سعد قال، حدثني أبي قال، حدثني عمي قال، حدثني أبي، عن أبيه، عن ابن عباس قوله: " لعن الذين كفروا من بني إسرائيل على لسان داود وعيسى ابن مريم " قال: لعنوا بكل لسان: لعنوا على عهد موسى في التوراة، ولعنوا على عهد داود في الزبور، ولعنوا على عهد عيسى في الإنجيل، ولعنوا على عهد محمد صلى الله عليه وسلم في القرآن

Ibn Abbaas said: They were cursed by every tongue. They were cursed during the reign of Moses in the Tawrah. And they were cursed during the reign of Daawud in the Zaboor. And the were cursed during the reign of Jesus in the Injeel. And they were cursed during the reign of Muhammad (sallallaahu 'alayhi wa sallam) in the Qur'aan. 

حدثنا ابن وكيع قال، حدثنا جرير، عن حصين، عن مجاهد:"لعن الذين كفروا من بني إسرائيل على لسان داود وعيسى ابن مريم"، قال: لعنوا على لسان داود فصاروا قردة، ولُعنوا على لسان عيسى فصاروا خنازيرَ

Mujaahid said: They were cursed by the tongue of Daawud, and consequently turned into monkeys. And they were cursed by the tongue of Jesus, and consequently turned into pigs.