Jihad (Kitab Al-Jihad)
Dawud :: Book 14 : Hadith 2522
Narrated Abdullah ibn Amr ibn al-'As:
A man came to the Apostle of Allah (peace_be_upon_him) and said: I came to you to take the oath of allegiance to you on emigration, and I left my parents weeping. He (the Prophet) said: Return to them and make them laugh as you made them weep.