738/1 - Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah’s peace and blessings be upon him) said: “If anyone of you is invited, let him answer the invitation. If he is fasting, let him supplicate (for the inviter); and if he is not fasting, let him eat.” [Narrated by Muslim]
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1) The obligation to accept the invitation to a wedding banquet, whether the person is fasting or not.
2) Fasting does not prevent a person from attending the wedding banquet. Although he may not eat, he can still invoke Allah’s blessings upon the hosts.
The Prophet (may Allah’s peace and blessings be upon him) said: “A person observing voluntary fasting is in control of his affair. He can fast if he so wishes, and he can break his fast if he so wishes.” [Ahmad] We learn from this Hadīth
that it is permissible for a person observing voluntary fasting to break his fast if he is invited to a wedding banquet, especially if he intends by doing so to please the hosts.
The Prophet (may Allah’s peace and blessings be upon him) said: “The dearest among people to Allah are those who are most beneficial to people, and the dearest deed in the sight of Allah is joy that you bring to a Muslim, or that you relieve his distress, repay his debt, or satisfy his hunger. I would rather go with a brother of mine to fulfill some of his needs than to retire in this mosque - i.e. the mosque of Madīnah - for a month. If anyone goes with his brother to fulfill a need of his until he establishes it for him, Allah will make his feet established on the Sirāt (Bridge) on a day when feet will slip...” [Narrated by Ibn Abi al-Dunya in his book "Qadā’ Al-Hawā’ij"; reported by ‘Abdullāh ibn ‘Umar (may Allah be pleased with him and his father)]