1؎: The purpose of the people's question was that you have forbidden us from jest (laughter + joking) and being cheerful, yet you yourself display cheerfulness. That is why you replied that even at times of jest and cheerfulness, I do not say anything except the truth, whereas on such occasions other people may utter inappropriate and false things.
Explanation & Benefits
Shaykh Dr. Abdur Rahman Freywai
Explanation: 1: The purpose of the people's question was that you (sallallahu alayhi wa sallam) have forbidden us from jesting (humor) and lightheartedness, yet you yourself engage in lightheartedness. For this reason, you (sallallahu alayhi wa sallam) said that even at the time of jest and lightheartedness, I do not say anything except the truth, whereas on such occasions, other people may say inappropriate and untrue things.
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 1990