It is reported that ʿAlī – Allāh be pleased with him – said:
When you learn knowledge, preserve it, and do not mix it with laughter and falsehood, such that the hearts refuse (dislike) it.
Al-Khaṭīb Al-Baghdādī, Al-Jāmiʿ li-Akhlāq Al-Rāwī wa Ādāb Al-Sāmiʿ 1:232
It is reported that Mālik – Allāh have mercy on him – said:
It is upon whoever seeks knowledge to have a solemn, dignified demeanour, fearful [of Allāh]; and to follow in the footsteps of those who went before him.
ʿAbd Al-Raḥmān b. Mahdī reports:
A man laughed in [the circle of] Hishām Al-Dustawāʾī, so Hishām said to him, “Young man! You seek knowledge laughing?” He replied, “Is it not Allāh who makes [us] laugh and cry (as stated in the Qurʾān)?” So Hishām replied, “Then go and cry.”
Op. cit. 233
Ismāʿīl b. Yaḥyā reports:
Sufyān once saw me joking with a man from Banī Shaybah at the House (Kaʿbah). I laughed, so he said to me, “You laugh here? A man used to hear a single ḥadīth and its demeanour and guidance would be seen on him for three days.”
Op. cit. 234