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

الترغيب في الصدق والترهيب من الكذب

Encouragement to be honest and discouragement from being dishonest.

Source: al-Targhīb wal-Tarhīb 3/580

‘Ubadah ibn al-Samit reported: The Messenger of Allah, peace and blessings be upon him, said:

اضْمَنُوا لِي سِتًّا مِنْ أَنْفُسِكُمْ أَضْمَنْ لَكُمُ الْجَنَّةَ اصْدُقُوا إِذَا حَدَّثْتُمْ وَأَوْفُوا إِذَا وَعَدْتُمْ وَأَدُّوا إِذَا اؤْتُمِنْتُمْ وَاحْفَظُوا فُرُوجَكُمْ وَغُضُّوا أَبْصَارَكُمْ وَكُفُّوا أَيْدِيَكُمْ

Guarantee for me six deeds and I will guarantee for you Paradise: Be truthful when you speak, keep your promises when you make them, fulfill the trust when you are trusted, guard your chastity, lower your gaze, and restrain your hands from harming others.

Source: Musnad Aḥmad 22251, Grade: Sahih li ghayri

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

تَقَبَّلُوا لِي سِتًّا أَتَقَبَّلْ لَكُمْ بِالْجَنَّةِ إِذَا حَدَّثَ أَحَدُكُمْ فَلا يَكْذِبْ وَإِذَا وَعَدَ فَلا يُخْلِفْ وَإِذَا اؤْتُمِنَ فَلا يَخُنْ وَغُضُّوا أَبْصَارَكُمْ وَكُفُّوا أَيْدِيَكُمْ وَاحْفَظُوا فُرُوجَكُمْ

Accept six deeds from me and I assure your acceptance into Paradise. When one of you speaks, let him not lie. When one of you promises, let him not break it. When one of you is trusted, let him not betray it. Lower your gaze, restrain your hands from harming others, and guard your chastity.

Source: Musnad Abī Ya’lá 4195, Grade: Sahih

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

أَنَا زَعِيمٌ بِبَيْتٍ فِي رَبَضِ الْجَنَّةِ لِمَنْ تَرَكَ الْمِرَاءَ وَإِنْ كَانَ مُحِقًّا وَبِبَيْتٍ فِي وَسَطِ الْجَنَّةِ لِمَنْ تَرَكَ الْكَذِبَ وَإِنْ كَانَ مَازِحًا وَبِبَيْتٍ فِي أَعْلَى الْجَنَّةِ لِمَنْ حَسَّنَ خُلُقَهُ

I guarantee a house on the outskirts of Paradise for one who leaves arguments even if he is right, and a house in the middle of Paradise for one who abandons lies even when joking, and a house in the highest part of Paradise for one who makes his character excellent.

Source: Sunan Abī Dāwūd 4800, Grade: Sahih

Ibn Abi Qurad reported: The Prophet, peace and blessings be upon him, said:

مَنْ سَرَّهُ أَنْ يُحِبَّ اللَّهَ وَرَسُولَهُ أَوْ يُحِبَّهُ اللَّهُ وَرَسُولُهُ فَلْيَصْدُقْ حَدِيثَهُ إِذَا حَدَّثَ وَلْيُؤَدِّ أَمَانَتَهُ إِذَا ائْتُمِنَ وَلْيُحْسِنْ جِوَارَ مَنْ جَاوَرَهُ

Whoever is pleased to love Allah and his messenger, or to be loved by Allah and his messenger, let him be truthful when he speaks, let him fulfill the trust to whom it is due, and let him treat well anyone who would be his neighbor.

Source: Shu’ab al-Imān 1439, Grade: Hasan

Abdullah ibn Amr reported: The Messenger of Allah, peace and blessings be upon him, said:

أَرْبَعٌ إِذَا كُنَّ فِيكَ فَلَا عَلَيْكَ مَا فَاتَكَ مِنْ الدُّنْيَا حِفْظُ أَمَانَةٍ وَصِدْقُ حَدِيثٍ وَحُسْنُ خَلِيقَةٍ وَعِفَّةُ طُعْمَةٍ

If you have these four qualities, you will not worry about what you missed in the world: fulfilling the trust, truthful speech, good character, and restraint with food.

Source: Musnad Aḥmad 6614, Grade: Sahih

Hasan ibn Ali reported: The Messenger of Allah, peace and blessings be upon him, said:

دَعْ مَا يَرِيبُكَ إِلَى مَا لَا يَرِيبُكَ فَإِنَّ الصِّدْقَ طُمَأْنِينَةٌ وَإِنَّ الْكَذِبَ رِيبَةٌ

Leave what makes you doubt for what does not make you doubt. Verily, truth brings peace of mind and falsehood sows doubt.

Source: Sunan al-Tirmidhī 2518, Grade: Sahih

Abdullah ibn Amr reported: I said, “O Messenger of Allah, who are the best people?” The Messenger of Allah, peace and blessings be upon him, said:

ذُو الْقَلْبِ الْمَخْمُومِ وَاللِّسَانِ الصَّدُوقِ

One with a heart swept clean and truthful in speech.

We said, “O Messenger of Allah, we know truthful in speech. What is a heart swept clean?” The Prophet said:

هُوَ التَّقِيُّ النَّقِيُّ لا إِثْمَ فِيهِ وَلا بَغْيَ وَلا حَسَدَ

One that is mindful of Allah and pure, in which there is no sin, nor aggression, nor envy.

We said, “Who shows a sign of it?” The Prophet said:

الَّذِي يَشْنَأُ الدُّنْيَا وَيُحِبُّ الآخِرَةَ

One who hates worldliness and loves the Hereafter.

They said, “And who shows a sign of it?” The Prophet said:

مُؤْمِنٌ فِي خُلُقٍ حَسَنٍ

A believer with good character.

Source: Shu’ab al-Imān 4457, Grade: Sahih

Abdullah ibn Mas’ud reported: The Messenger of Allah, peace and blessings be upon him, said:

عَلَيْكُمْ بِالصِّدْقِ فَإِنَّ الصِّدْقَ يَهْدِي إِلَى الْبِرِّ وَإِنَّ الْبِرَّ يَهْدِي إِلَى الْجَنَّةِ وَمَا يَزَالُ الرَّجُلُ يَصْدُقُ وَيَتَحَرَّى الصِّدْقَ حَتَّى يُكْتَبَ عِنْدَ اللَّهِ صِدِّيقًا وَإِيَّاكُمْ وَالْكَذِبَ فَإِنَّ الْكَذِبَ يَهْدِي إِلَى الْفُجُورِ وَإِنَّ الْفُجُورَ يَهْدِي إِلَى النَّارِ وَمَا يَزَالُ الرَّجُلُ يَكْذِبُ وَيَتَحَرَّى الْكَذِبَ حَتَّى يُكْتَبَ عِنْدَ اللَّهِ كَذَّابًا

You must be truthful. Verily, truthfulness leads to righteousness and righteousness leads to Paradise. A man continues to be truthful and encourages honesty until he is recorded with Allah as truthful. Beware of falsehood. Verily, falsehood leads to wickedness and wickedness leads to the Hellfire. A man continues tell lies and encourages falsehood until he is recorded with Allah as a liar.

Source: Ṣaḥīḥ al-Bukhārī 5743, Grade: Muttafaqun Alayhi

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

عَلَيْكُمْ بِالصِّدْقِ فَإِنَّهُ مَعَ الْبِرِّ وَهُمَا فِي الْجَنَّةِ وَإِيَّاكُمْ وَالْكَذِبَ فَإِنَّهُ مَعَ الْفُجُورِ وَهُمَا فِي النَّارِ وَسَلُوا اللَّهَ الْمُعَافَاةَ فَإِنَّهُ لَمْ يُؤْتَ أَحَدٌ بَعْدَ الْيَقِينِ خَيْرًا مِنَ الْمُعَافَاةِ وَلَا تَحَاسَدُوا وَلَا تَبَاغَضُوا وَلَا تَقَاطَعُوا وَلَا تَدَابَرُوا وَكُونُوا عِبَادَ اللَّهِ إِخْوَانًا

You must be truthful, for it is alongside righteousness and they are both in Paradise. Beware of falsehood, for it is alongside wickedness and they are both in the Hellfire. Ask Allah for wellness, for no one is given anything better after conviction than wellness. Do not envy each other, do not hate each other, do not cut each other off, and do not turn away from each other. Be servants of Allah as brothers.

Source: Sunan Ibn Mājah 3847, Grade: Sahih

Mu’awiyah ibn Abi Sufyan reported: The Messenger of Allah, peace and blessings be upon him, said:

عَلَيْكُمْ بِالصِّدْقِ فَإِنَّهُ يَهْدِي إِلَى الْبِرِّ وَهُمَا فِي الْجَنَّةِ وَإِيَّاكُمْ وَالْكَذِبَ فَإِنَّهُ يَهْدِي إِلَى الْفُجُورِ وَهُمَا فِي النَّا

You must be truthful. Verily, it leads to righteousness and they are both in Paradise. Beware of dishonesty, for it leads to wickedness and they are both in the Hellfire.

Source: al-Mu’jam al-Kabīr 894, Grade: Sahih li ghayrihi

Samurah ibn Jundub reported: The Prophet, peace and blessings be upon him, said:

رَأَيْتُ اللَّيْلَةَ رَجُلَيْنِ أَتَيَانِي قَالَا الَّذِي رَأَيْتَهُ يُشَقُّ شِدْقُهُ فَكَذَّابٌ يَكْذِبُ بِالْكَذْبَةِ تُحْمَلُ عَنْهُ حَتَّى تَبْلُغَ الْآفَاقَ فَيُصْنَعُ بِهِ إِلَى يَوْمِ الْقِيَامَةِ

I saw a dream at night in which two men came to me. They said: The one whose face you saw being torn away was great liar, who would tell a lie and it would be carried until it reaches the horizons. This will be done to him until the Day of Resurrection.

Source: Ṣaḥīḥ al-Bukhārī 5745, Grade: Sahih

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

مِنْ عَلَامَاتِ الْمُنَافِقِ ثَلَاثَةٌ وَإِنْ صَامَ وَصَلَّى وَزَعَمَ أَنَّهُ مُسْلِمٌ إِذَا حَدَّثَ كَذَبَ وَإِذَا وَعَدَ أَخْلَفَ وَإِذَا اؤْتُمِنَ خَانَ

Among the signs of a hypocrite are three, even if he fasts and prays and claims to be a Muslim: when he speaks he lies, when he gives a promise he breaks it, and when he is trusted he betrays.

Source: Ṣaḥīḥ al-Bukhārī 33, Grade: Muttafaqun Alayhi

Abdullah ibn Amr reported: The Messenger of Allah, peace and blessings be upon him, said:

أَرْبَعٌ مَنْ كُنَّ فِيهِ كَانَ مُنَافِقًا خَالِصًا وَمَنْ كَانَتْ فِيهِ خَلَّةٌ مِنْهُنَّ كَانَتْ فِيهِ خَلَّةٌ مِنْ نِفَاقٍ حَتَّى يَدَعَهَا إِذَا حَدَّثَ كَذَبَ وَإِذَا عَاهَدَ غَدَرَ وَإِذَا وَعَدَ أَخْلَفَ وَإِذَا خَاصَمَ فَجَرَ

There are four signs that make someone a pure hypocrite and whoever has them has a characteristic of hypocrisy until he abandons it: when he speaks he lies, when he makes a covenant he is treacherous, when he makes a promise he breaks it, and when he argues he is wicked.

Source: Ṣaḥīḥ al-Bukhārī 34, Grade: Muttafaqun Alayhi

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

ثَلاثٌ مَنْ كُنَّ فِيهِ فَهُوَ مُنَافِقٌ وَإِنْ صَامَ وَصَلَّى وَحَجَّ وَاعْتَمَرَ وَقَالَ إِنِّي مُسْلِمٌ إِذَا حَدَّثَ كَذَبَ وَإِذَا وَعَدَ أَخْلَفَ وَإِذَا اؤْتُمِنَ خَانَ

Whoever has three traits is a hypocrite, even if he fasts, prays, goes to Hajj and Umrah, and claims to be a Muslim. When he speaks, he lies. When he promises, he breaks it. When he is trusted, he betrays it.

Source: Musnad Abī Ya’lá 4039, Grade: Hasan li ghayrihi

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

لَا يُؤْمِنُ الْعَبْدُ الْإِيمَانَ كُلَّهُ حَتَّى يَتْرُكَ الْكَذِبَ فِي الْمُزَاح وَالْمِرَاءَ وَإِنْ كَانَ صَادِقًا

Verily, the servant does not entirely have faith until he abandons lying even while joking, and he abandons arguing even if he is correct.

Source: Musnad Aḥmad 8566, Grade: Sahih li ghayrihi

Aisha, may Allah be pleased with her, said:

مَا كَانَ خُلُقٌ أَبْغَضَ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مِنْ الْكَذِبِ وَلَقَدْ كَانَ الرَّجُلُ يُحَدِّثُ عِنْدَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِالْكِذْبَةِ فَمَا يَزَالُ فِي نَفْسِهِ حَتَّى يَعْلَمَ أَنَّهُ قَدْ أَحْدَثَ مِنْهَا تَوْبَةً

There was no behavior more hateful to the Messenger of Allah, peace and blessings be upon him, than dishonesty. A man would tell a lie when speaking in the presence of the Prophet and he would not be satisfied until he knew that he had repented.

Source: Sunan al-Tirmidhī 1973, Grade: Sahih

Mu’awiyyah ibn Haydah reported: The Messenger of Allah, peace and blessings be upon him, said:

وَيْلٌ لِلَّذِي يُحَدِّثُ فَيَكْذِبُ لِيُضْحِكَ بِهِ الْقَوْمَ وَيْلٌ لَهُ وَيْلٌ لَهُ

Woe to one who tells lies to make people laugh. Woe to him! Woe to him!

Source: Sunan Abī Dāwūd 4990, Grade: Hasan

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

ثَلَاثَةٌ لَا يُكَلِّمُهُمْ اللَّهُ يَوْمَ الْقِيَامَةِ وَلَا يُزَكِّيهِمْ وَلَا يَنْظُرُ إِلَيْهِمْ وَلَهُمْ عَذَابٌ أَلِيمٌ شَيْخٌ زَانٍ وَمَلِكٌ كَذَّابٌ وَعَائِلٌ مُسْتَكْبِرٌ

There are three to whom Allah will not speak on the Day of Resurrection, nor will he purify them, nor will he look at them, and they will have an agonizing punishment: an old man who commits adultery, a king who lies, and an arrogant dependent.

Source: Ṣaḥīḥ Muslim 107, Grade: Sahih

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

ثَلاثَةٌ لا يَدْخُلُونَ الْجَنَّةَ الشَّيْخُ الزَّانِي وَالإِمَامُ الْكَذَّابُ وَالْعَائِلُ الْمَزْهُوُّ

Three people will not enter Paradise: an elderly person who commits adultery, a dishonest leader, and a conceited dependent.

Source: Musnad al-Bazzār 2235, Grade: Sahih