Some people joke too much and it becomes a habit for them. This is the opposite of the serious nature which is the characteristic of the believers. Joking is a break, a rest from ongoing seriousness and striving; it is a little relaxation for the soul.
>>"Umar ibn ‘Abd al-‘Azeez (may Allah have mercy on him) said:“Fear joking, for it is folly and generates grudges.”
>>Imam al-Nawawi (may Allah have mercy on him) said:“The kind of joking which is forbidden is that which is excessive and persistent, for it leads to too much laughter and hardening of the heart, it distracts from remembrance of Allah, and it often leads to hurt feelings, generates hatred and causes people to lose respect and dignity. But whoever is safe from such dangers, then that which the Messenger of Allah (peace and blessings of Allah be upon him) used to do is permissible for him.”
>>Sa’d ibn Abi Waqqas said:“Set a limit to your jokes, for going to extremes makes you lose respect and incites the foolish against you".
>>The Prophet (peace and blessings of Allah be upon him) said:“Do not laugh too much, for laughing too much deadens the heart.” (Saheeh al-Jami’, 7312)
>>"Umar ibn al-Khattab (may Allah be pleased with him) said:“Whoever laughs too much or jokes too much loses respect, and whoever persists in doing something will be known for it.”
>>A man said to Sufyaan ibn ‘Uyaynah (may Allah be pleased with him),“Joking is not right, it is to be denounced.” He replied,“Rather it is Sunnah, but only for those who know how to do it and do it at the appropriate time.”
>>The Prophet (peace and blessings of Allah be upon him) said:“If you knew what I know, you would laugh little and weep much.” In Fath al-Baari it says: “What is meant by knowledge here has to do with the might of Allah and His vengeance upon those who disobey Him, and the terrors that occur at death, in the grave and on the Day of Resurrection.”
So beware of joking, for it“causes a person to lose face after he was thought of as respectable, and it brings him humiliation after esteem.”