Abu Huraira reported God's Messenger as saying, “The invitations of two people who are rivalling one another should not be accepted, and the food they provide should not be eaten.” The imam Ahmad said it means two people who are competing with one another in providing a feast out of self-glory and ostentation.
Abu Huraira reported the Prophet as saying, “When one of you visits his brother Muslim he should eat of his food without asking questions and drink from what he provides without asking questions.”
Baihaqi transmitted the three traditions in Shu'ab al-iman, saying that if is sound, it is because a Muslim would obviously give him only food and drink which were lawful in his opinion.