Hazrat Abdullah ibn Umar (Radiyallahu anhu) narrates that the Holy Prophet (صلى الله عليه وسلم) said:
“The person who is invited amongst you by his brother should accept the invitation whether it is a wedding invitation or anything similar to it.” [Muslim]
Hazrat Jabir ibn Abdullah (radiallahu anhu) narrates that the Holy Prophet (صلى الله عليه وسلم) said:
“If anyone of you is invited to partake of meals, he should at least accept the invitation. Thereafter he may partake of it if he desires or he may totally abstain from it.” [Muslim]
Hazrat Abu Hurairah (radiallahu anhu) narrates that the Holy Prophet (صلى الله عليه وسلم) said:
“If anyone of you is invited for meals, he should accept the invitation. If he is fasting, he should make Duaa (of goodness and blessing) for the inviter (some maintain that he should set out and perform salaah at the host’s house), and if he is not fastin he should partake of the meal.” [Muslim]
No excuse will be entertained in declining an invitation. However, if wine and other intoxicants are provided at the invitation or food will be eaten out of gold and silver utensils or there is a fear of any other evil, one should on no account accept the invitation.
If uninvited people accompany one who is invited, he should firstly seek the host’s consent so that he is not annoyed and disheartened (by the arrival of an uninvited guest).
Hazrat Abu Masood Badri (radiallahu anhu) narrates: A certain person invited the Holy Prophet صلى الله عليه وسلم over for meals. Including the Prophet صلى الله عليه وسلم, food was prepared for 5 people. On the way to the invitation, a sixth person joined them. When the group arrived at the door of the host, the Holy Prophet صلى الله عليه وسلم said:
“This person has also joined us. if you wish to, you may permit him or else he will return.”
He (the host) said:
“O Prophet of Allah صلى الله عليه وسلم, I don’t mind him partaking of the meal.” [Muslim]
Hazrat Abdullah ibn Masood (radiallahu anhu) says that the Holy Prophet (صلى الله عليه وسلم) said:
“Accept the invitation of he who invites you. Avoid declining a gift and refrain from annoying the Muslims.” [Muslim]
Source: The 40 Pathways to Jannah by Sheikh Khalid Sayyid Ali