It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Accept the invitation of the one who invites, do not return a gift, and do not strike people (or: Muslims)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10406