Abu Hurairah (May Allah be pleased with him) reported: Messenger of Allah (PBUH) said, "When any of you is invited to a meal, he should accept the invitation. If he is observing Saum (fasting), he should supplicate for the betterment of the host and if he is not fasting, he should eat."[Muslim].
Shari`ah permits a person to break a voluntary fasting. The example of Messenger of Allah (PBUH) clearly shows that it is not binding on him to keep it again as a redeeming step. A man is, therefore, free to break his voluntary fasting and participate in the feast to which he is invited. However, if somebody is reluctant to break the fast, he should pray for the good and welfare of the host. But we should refuse to attend such treats which are flagrantly masked by extravagance and frivolous un-Islamic rites to the disobedience of Allah.