A Glimpse at Humor in the Prophetic Sunnah By Abu al-Hasan Malik Adam al-Akhdar
On the authority of Abu Hurayrah (may Allah be pleased with him) who said that some of the Companions asked the Prophet (peace be upon him): "O Messenger of Allah, is it that you joke with us? he answered: "Yes, except that I only say that which is true."
Sufyan al-Thawri (d. 167H) (May Allah have mercy on him) was asked: Is joking considered a shortcoming?" He replied: "No, rather, it is sunnah"