The Messenger of Allah ﷺ said, "If you knew what I know, you would laugh little and weep much."
حدثنا محمد بن المثنى حدثنا عبد الصمد بن عبد الوارث حدثنا همام عن قتادة
قال رسول الله ﷺ لو تعلمون ما أعلم لضحكتم قليلا ولبكيتم كثيرا
Takhrij, sahih. Ahmad narrated it in 3/210 from Abdul-Samad, with this wording. Mawla bin Anas also narrated it (Bukhari and Muslim), as did Abu Talha Asadi (Ahmad, 3/180), both of them from Anas, with this wording.