بسم الله الرحمن الرحيم
The Messenger of Allah ﷺ said:
لا تكثر الضحك فإن كثرة الضحك تميت القلب
“Do not laugh too much, for too much laughter deadens the heart.” 
The consequences of a dead heart are extremely dire, as some scholars identified it to be “root” of all punishments (due to what is mentioned in Al-Baqarah 74 for example). From a hardened or dead heart rises every type of negative characteristic. One such risk of excessive laughter is highlighted by Ibn Hibban, who said of mazâh:
و كم من افتراق بين أخوين و هجران بين متآلفين كان أول ذلك المزاح
“And how much of division (and breakup) has occurred between brothers and desertion among (those who were previously) harmoniously close, the first (cause) of which is due to mazâh.” 
Ibraheem an-Nakha’i said: لا يمازحك إلا من يحبك
“Do not Mazâh around except with those whom you are beloved to.” 
And the reasons for this are obvious. One who loves you will tolerate your antics.
المزاح (Al-Mazâh) is something that includes joking, humourism and jesting; it also denotes practical jokes. And when the limits and conditions of mazâh are exceeded, it usually leads to souring of relationships and even ruination because of abuse and hatred it risks breeding. Imam Al-Nawawi said it aptly in his ‘Al-Adhkar’, (p.390) that:
المزاح المنهي عنه هو الذي فيه إفراط ويداوم عليه ، فإنه يورث الضحك وقسوة القلب ويشغل عن ذكر الله تعالى ويؤول في كثير من الأوقات إلى الإيذاء ، ويورث الأحقاد ، ويسقط المهابة والوقار ، فأما من سلم من هذه الأمور فهو المباح الذي كان رسول الله ﷺ يفعله
“Al-Mazâh that is forbidden is what is excessive and persistent, which leads to (much) laughter and hardens the heart, which distracts from the remembrance of Allah Almighty; and is given to much abuse and breeds hatred, and what diminishes one’s prestige and dignity. Thus it was to be safe from such things that the Messenger ﷺ would permit actions (to the contrary).”
What is not recommended is making people laugh using false speech or making it a regular habit of a person, otherwise it isn’t to be detested; for the Messenger ﷺ used to laugh until his premolars appeared. Seeking comfort in such thing every now and then is like adding salt in the cooking pot (to enhance flavour). The Companions too, used to enjoy lighter moments and laugh, yet they were the firmest of men of faith and understood moderation and the proportionate wisdom behind humour.
Ibn Is-haq conveyed that Al-Zuhri would teach knowledge, and then afterwards end his gathering by saying, “Bring forth your humour. Bring forth your poetry. Engage in some of what amuses you and increases your jovial mood, for the ears are no longer absorbing (serious knowledge) and the hearts are unstable.” Malik ibn Dinar said, “When people before you got weary of serious talk, they would say, ‘the ears are desorbing and the hearts are sour, so bring forth your funny stories.'” Abu Zayd said that his father told him, “Ataa’ ibn Yasar would talk to me and Abu Hazim until we would weep; then he would (lighten the mood by) talk to us until we would laugh.” Then he added, “Once like this, and once like that.” 
A man once said to Sufyan ibn ‘Uyaynah:
المزاح هجنة أي مستنكر! فأجابه قائلاً : بل هو سنة ولكن لمن يُحسنه ويضعه في موضعه
“Al-Mazâh is faulty and should be denounced.” He replied, “Rather it is Sunnah, but only for those who know how to perfect it (and use it) at the appropriate time.” 
May Allah grant us a good clean sense of humour that strengthens bonds and makes people smile, for indeed putting a smile on the face of your brother is an easy charity.
 Al-Tirmidhi, 2305; graded as hasan by Al-Albani in ‘Saheeh al-Jaami’, 7435
 ‘Rawdatul Uqala’ (p.81)
 Rawdatul Uqala’, 1/80
 See Ibn Al-Jawzi, ‘Akhbar al-Hamqa’ for more on the suject matter
 Hilyat al-Awliya,