Hadith ~ a happy face

Abu Dharr said, "The Prophet, may Allah bless him and grant him peace, told me, 'Do not consider anything correct insignificant, even meeting your brother with a happy face." [Muslim]

Riyad as-Salihin (The Meadows of the Righteous) of Iman Mohieddine Annawawi 631-676.  Chapter 7: "On the clarification of the many paths of good", Hadith Number: 121.