1. The Messenger of Allah ﷺ said, “Kind speech and feeding (the hungry) guarantee you Paradise.” (al-Tabarani)

2. “And speak nicely to people.” (Qur’an, 2:83)

3. “When you are greeted with a greeting, greet in return with what is better than it, or (at least) return it equally.” (Qur’an, 4:86) Ibn Abbas commented on this and said, “He who greets you return his greeting in better words even if he were a Magian.1 He also said, “If Pharoah were to speak nicely to me, I would do so to him.”

4. Anas (ra) narrated that the Messenger of Allah ﷺ said, “Verily there are chambers in Paradise; their insides and outsides can be seen – for him who spoke kindly and fed (the hungry).” (al-Tirmidhi)

5. He ﷺ also said, “A good word is also a charitable deed.” (Muslim)

6. “Ward off the Fire even if by giving half a date in charity. If you could not afford that then utter a kind word.” (al-Bukhari and Muslim)

7. `Umar (ra) said, “Generosity is an easy thing. It is a smiling face and kind words.”

8. Some wise men said, “Do not be stingy with a word that does not arouse your Lord’s wrath yet it pleases your brother. It may happen that Allah gives you the reward of those who do good works.”

9. “And let not those among you who are blessed with graces and wealth swear not to give to their kinsmen, the poor, and those who left their homes for Allah’s cause. Let them pardon and forgive. Do you not wish that Allah should forgive you?” (Qur’an, 24:22). Abu Bakr (ra) had cut off his financial support of his relative Mustah because Mustah had participated in the slander against his daughter `A’ishah (ra). After this verse was revealed, he resumed and even increased the amount he gave Mustah in financial support.

10. “Show forgiveness, enjoin what is good, and turn away from the foolish.” (Qur’an, 7:199)

http://www.suhaibwebb.com/personaldvlpt/character/30-reasons-to-avoid-being-an-angry-and-argumentative-person/