(a) It is narrated from Ibn Shihab (may Allah have mercy on him) that the Prophet (peace and blessings be upon him) ordered a man who had laughed in prayer "to repeat the ablution and the prayer."
(b) It is narrated from al-Hasan (may Allah have mercy on him) that he did not hold that laughing in prayer requires ablution.
(c) It is narrated from al-Zuhri (may Allah have mercy on him): Because of laughing, one repeats the prayer but does not repeat the ablution.
Imam al-Shafi'i (may Allah have mercy on him) said: We did not accept this narration because it is mursal. The Shaykh said: All these narrations go back to Abu al-Aliyah al-Riyahi. Abd al-Rahman bin Mahdi (may Allah have mercy on him) said: The hadith about laughing in prayer, that the Prophet (peace and blessings be upon him) ordered him to repeat the ablution and the prayer, all revolves around Abu al-Aliyah. Ibn Adi (may Allah have mercy on him) said: The main thing held against Abu al-Aliyah is this hadith, and all the others who narrated it ultimately rely on Abu al-Aliyah. Sulayman bin Harb (may Allah have mercy on him) declared this hadith weak. Yahya bin Ma'in (may Allah have mercy on him) said: The mursal reports of Ibrahim are sound, except the hadith of the merchant of Bahrain and the hadith of laughing in prayer, and the mursal report of al-Zuhri carries no weight. The Shaykh said: It has also been narrated with connected chains, but they are weak. Muhammad bin Yahya al-Dhuhli (may Allah have mercy on him) said: No report about laughing in prayer is established from the Prophet (peace and blessings be upon him), and the hadith of Abu al-Aliyah and its supporting narrations are flimsy and weak.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 682