Shaikh Bin Baz rahimahullah said:
Question: What is the ruling on laughing in prayer? If the one who laughs in prayer have to repeat the prayer?
Answer: “Laughing the prayer invalidates the prayer according to consensus of the people of knowledge. If he laughs in prayer it is invalid. Likewise, if he spoke deliberately in his prayer except if he was ignorant or it was forgetfully. So the prayer is not invalidated by forgetful speech or speech due to ignorance. However, laughing invalidates the prayer because it is playing in it and mockery. We ask Allah for well being” [https://www.binbaz.org.sa/fatawa/4478]
The Permanent Committee said:
Question: What is the ruling on laughing in prayer, whether he did not know it invalidates the prayer or he knew?
Answer: “Laughing in the prayer is not allowed whether he knows laughing invalidates the prayer or not. It invalidates the prayer by consensus.
With Allah is Tawfeeq and may peace and blessings be upon our Prophet Muhammad, his followers, and Companions”
[https://www.alifta.net/Fatawa/fatawaDetails.aspx?BookID=3&View=Page&PageNo=1&PageID=2263]
Translated by
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan
Assalaamu alaykum wa rahmatulahi wa barakaatuh. What is the proof to say it invalidates the Salaah? They didn’t provide any proof….
Alayka salam wa rahmatullahi wa barakatuhu,
The proof for this is the following narration reported from Jabir (may Allah be pleased with him):
من ضحك في الصلاة أعاد الصلاة ولم يعد الوضوء
“Whoever laughs in prayer must repeat the prayer and not repeat the wudu”
[Graded Saheeh by al-Albani in Irwaa al-Ghaleel (2/114)]
I hope that helps
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan