Al-Mundhiri recorded the following chapter in his book Al-Targhib wal-Tarhib:

الترهيب من الغيبة والبَهت والترغيب في ردهما

Discouragement of backbiting and slander, and encouragement to defend against them both.

Source: al-Targhīb wal-Tarhīb 3/512

Abu Bakrah reported: The Prophet, peace and blessings be upon him, said in the farewell sermon:

إِنَّ دِمَاءَكُمْ وَأَمْوَالَكُمْ وَأَعْرَاضَكُمْ عَلَيْكُمْ حَرَامٌ كَحُرْمَةِ يَوْمِكُمْ هَذَا فِي شَهْرِكُمْ هَذَا أَلَا لِيُبَلِّغ الشَّاهِدُ مِنْكُمْ الْغَائِبَ

Verily, your lives, your property, and your reputations have been made sacred to you, just as the sanctity of this day of yours, in this month of yours. Will not the witness inform the absent?

Source: Ṣaḥīḥ al-Bukhārī 105, Grade: Muttafaqun Alayhi

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

كُلُّ الْمُسْلِمِ عَلَى الْمُسْلِمِ حَرَامٌ دَمُهُ وَمَالُهُ وَعِرْضُهُ

The entirety of the Muslim is sacred to another Muslim: his life, his wealth, and his reputation.”

Source: Ṣaḥīḥ Muslim 2564, Grade: Sahih

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

أَتَدْرُونَ مَا الْغِيبَةُ

Do you know what backbiting is?

They said, “Allah and his messenger know best.” The Prophet said:

ذِكْرُكَ أَخَاكَ بِمَا يَكْرَهُ

To mention your brother in a way he dislikes.

It was said, “What do you think if what I said about him is true?” The Prophet said:

إِنْ كَانَ فِيهِ مَا تَقُولُ فَقَدْ اغْتَبْتَهُ وَإِنْ لَمْ يَكُنْ فِيهِ فَقَدْ بَهَتَّهُ

If what you say about him is true, it is backbiting. If it is not true, it is slander.

Source: Ṣaḥīḥ Muslim 2589, Grade: Sahih

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

إِنَّ مِنْ أَكْبَرِ الْكَبَائِرِ اسْتِطَالَةَ الْمَرْءِ فِي عِرْضِ رَجُلٍ مُسْلِمٍ بِغَيْرِ حَقٍّ وَمِنْ الْكَبَائِرِ السَّبَّتَانِ بِالسَّبَّةِ

Verily, among the worst of major sins is to attack the reputation of a Muslim man without just cause, and among major sins is to insult twice in response to one insult.

Source: Sunan Abī Dāwūd 4877, Grade: Hasan

Al-Bara’ ibn ‘Azib reported: The Messenger of Allah, peace and blessings be upon him, said:

الرِّبَا اثْنَانِ وَسَبْعُونَ بَابًا أَدْنَاهَا مِثْلُ إِتْيَانِ الرَّجُلِ أُمَّهُ وَأَرْبَى الرِّبَا اسْتِطَالَةُ الرَّجُلِ فِي عِرْضِ أَخِيهِ

Usury has seventy-two doors, the least of which is like a man who goes into his mother. The worst act of usury is for a man to attack the reputation of his brother.

Source: al-Mu’jam al-Awsaṭ 7151, Grade: Sahih li ghayrihi

Sa’id ibn Zayd reported: The Prophet, peace and blessings be upon him, said:

إِنَّ مِنْ أَرْبَى الرِّبَا الِاسْتِطَالَةَ فِي عِرْضِ الْمُسْلِمِ بِغَيْرِ حَقٍّ

Verily, the worst act of usury is to attack the reputation of a Muslim without a just cause.

Source: Sunan Abī Dāwūd 4876, Grade: Sahih

Aisha reported: I said to the Prophet, peace and blessings be upon him, “Such is enough for Safiyyah,” making fun of her short stature. The Prophet said:

لَقَدْ قُلْتِ كَلِمَةً لَوْ مُزِجَتْ بِمَاءِ الْبَحْرِ لَمَزَجَتْهُ

You have said a word that would pollute the water of the sea if mixed with it.

Source: Sunan Abī Dāwūd 4875, Grade: Sahih

Abdullah ibn Amr reported: They mentioned a man in front of the Messenger of Allah, peace and blessings be upon him, and they said, “He only eats if he is fed! He only moves if he is made to move!” The Prophet said:

اغْتَبْتُمُوهُ

You have backbitten him.

They said, “We only said what is true about him.” The Prophet said:

فَحَسْبُكَ إِذَا ذَكَرْتَ أَخَاكَ بِمَا فِيهِ

It is enough sin to mention bad things about your brother.

Source: Musnad ‘Abd Allāh ibn al-Mubārak 2, Grade: Hasan

In another narration, the Prophet said:

إِنْ قُلْتُمْ مَا لَيْسَ فِيهِ فَقَدْ بَهَتُّمُوهُ

If what you said about him were not true, you would have slandered him.

Source: al-Mu’jam al-Kabīr 57, Grade: Hasan li ghayrihi

Abdullah ibn Mas’ud reported: We were sitting with the Prophet, peace and blessings be upon him, when a man stood to leave, then another man spoke badly about him after he left. The Prophet said:

تَخَلَّلْ

Pick your teeth.

The man said, “O Messenger of Allah, why should I pick my teeth when I have not eaten meat?” The Prophet said:

إِنَّكَ أَكَلْتَ لَحْمَ أَخِيكَ

You have eaten the flesh of your brother.

Source: al-Mu’jam al-Kabīr 9951, Grade: Sahih

Qays reported: ‘Amr ibn al-‘As, may Allah be pleased with him, passed by the carcass of a dead mule and he said to his companions:

لأَنْ يَأْكُلْ أَحَدُكُمْ مِنْ هَذَا حَتَّى يَمْلَأَ بَطْنَهُ خَيْرٌ مِنْ أَنْ يَأْكُلَ لَحْمَ أَخِيهِ الْمُسْلِمِ

That one of you eat from this until his belly is full is better than to eat the flesh of his brother Muslim.

Source: Muṣannaf Ibn Abī Shaybah 24950, Grade: Sahih

Anas ibn Malik reported: The Messenger of Allah, peace and blessings be upon him, said:

لَمَّا عُرِجَ بِي مَرَرْتُ بِقَوْمٍ لَهُمْ أَظْفَارٌ مِنْ نُحَاسٍ يَخْمُشُونَ وُجُوهَهُمْ وَصُدُورَهُمْ فَقُلْتُ مَنْ هَؤُلَاءِ يَا جِبْرِيلُ قَالَ هَؤُلَاءِ الَّذِينَ يَأْكُلُونَ لُحُومَ النَّاسِ وَيَقَعُونَ فِي أَعْرَاضِهِمْ

When I was taken on my night journey, I passed by people who had metal hooks in their hands and they were clawing at their faces and necks. I said: Who are these, O Gabriel? Gabriel said: These are the ones who ‘eat the flesh of people’ (49:12) and attack their honor.

Source: Sunan Abī Dāwūd 4878, Grade: Sahih

Jabir ibn Abdullah reported: We were with the Prophet, peace and blessings be upon him, when we detected a foul odor being carried by the wind. The Prophet said, “

أَتَدْرُونَ مَا هَذِهِ الرِّيحُ هَذِهِ رِيحُ الَّذِينَ يَغْتَابُونَ الْمُؤْمِنِينَ

Do you know what this wind is? It is the smell of those who backbite the believers.

Source: Musnad Aḥmad 14370, Grade: Hasan

Abu Bakrah reported: The Prophet, peace and blessings be upon him, passed by two graves and he said:

إِنَّهُمَا لَيُعَذَّبَانِ وَمَا يُعَذَّبَانِ فِي كَبِيرٍ أَمَّا أَحَدُهُمَا فَيُعَذَّبُ فِي الْبَوْلِ وَأَمَّا الْآخَرُ فَيُعَذَّبُ فِي الْغَيْبَةِ

Verily, they are both being punished and not for something major. As for one, he is punished for the habit of soiling himself with urine. As for the other, he is punished for the habit of backbiting.

Source: Sunan Ibn Mājah 349, Grade: Sahih

Ya’la ibn Siyabah reported: He lived in the time of the Prophet, peace and blessings be upon him, and they came upon a grave whose occupant was being punished. The Prophet said:

إِنَّ هَذَا كَانَ يَأْكُلُ لُحُومَ النَّاسِ

Verily, this person used to eat the flesh of people.

Source: al-Mu’jam al-Awsaṭ 2434, Grade: Jayyid

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

أَتَدْرُونَ مَا الْمُفْلِسُ

Do you know who is bankrupt?

They said, “The one without money or goods is bankrupt.” The Prophet said:

إِنَّ الْمُفْلِسَ مِنْ أُمَّتِي يَأْتِي يَوْمَ الْقِيَامَةِ بِصَلَاةٍ وَصِيَامٍ وَزَكَاةٍ وَيَأْتِي قَدْ شَتَمَ هَذَا وَقَذَفَ هَذَا وَأَكَلَ مَالَ هَذَا وَسَفَكَ دَمَ هَذَا وَضَرَبَ هَذَا فَيُعْطَى هَذَا مِنْ حَسَنَاتِهِ وَهَذَا مِنْ حَسَنَاتِهِ فَإِنْ فَنِيَتْ حَسَنَاتُهُ قَبْلَ أَنْ يُقْضَى مَا عَلَيْهِ أُخِذَ مِنْ خَطَايَاهُمْ فَطُرِحَتْ عَلَيْهِ ثُمَّ طُرِحَ فِي النَّارِ

Verily, the bankrupt of my nation are those who come on the Day of Resurrection with prayers, fasting, and charity, but also with insults, slander, consuming wealth, shedding blood, and beating others. The oppressed will each be given from his good deeds. If his good deeds run out before justice is fulfilled, then their sins will be cast upon him and he will be thrown into the Hellfire.

Source: Ṣaḥīḥ Muslim 2581, Grade: Sahih

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

خَمْسٌ لَيْسَ لَهُنَّ كَفَّارَةٌ الشِّرْكُ بِاللَّهِ وَقَتْلُ النَّفْسِ بِغَيْرِ حَقٍّ وَبَهْتُ مُؤْمِنٍ وَفِرَارٌ يَوْمَ الزَّحْفِ وَيَمِينٌ صَابِرَةٌ يَقْتَطِعُ بِهَا مَالا بِغَيْرِ حَقٍّ

Five sins cannot be expiated: idolatry with Allah, killing a soul without a just case, slandering a believer, fleeing the battlefield, and bearing false witness to consume the wealth of another without right.

Source: Musnad al-Shāmiyyīn 1161, Grade: Hasan li ghayrihi

Abu Darda reported: The Prophet, peace and blessings be upon him, said:

مَنْ رَدَّ عَنْ عِرْضِ أَخِيهِ رَدَّ اللَّهُ عَنْ وَجْهِهِ النَّارَ يَوْمَ الْقِيَامَةِ

Whoever defends the reputation of his brother, Allah will defend his face from the Hellfire on the Day of Resurrection.

Source: Sunan al-Tirmidhī 1931, Grade: Sahih

Asma’ bint Yazid reported: The Messenger of Allah, peace and blessings be upon him, said:

مَنْ ذَبَّ عَنْ لَحْمِ أَخِيهِ فِي الْغِيبَةِ كَانَ حَقًّا عَلَى اللَّهِ أَنْ يُعْتِقَهُ مِنَ النَّارِ

Whoever defends the flesh of his brother from backbiting, it will be a duty upon Allah to free him from the Hellfire.

Source: Musnad Aḥmad 26950, Grade: Hasan

Anas reported: The Prophet, peace and blessings be upon him, said:

مَنْ نَصَرَ أَخَاهُ بِظَهْرِ الْغَيْبِ نَصَرَهُ اللَّهُ فِي الدُّنْيَا وَالْآخِرَةِ

Whoever supports his brother behind his back in his absence, Allah will support him in the world and in the Hereafter.

Source: al-Sunan al-Kubrá 16175, Grade: Sahih