The second reason is to honor his brother’s invitation when it is a wedding feast on its first day.

If, however, the invitation involves a munkar that you are unable to remove—such as pervasive cigarette smoke, a hookah, or unlawful music—it is impermissible for you to attend.

The scholars add an exception: if the objectionable act is taking place in a different area, while you have been invited to a place that is free of it, and the host is a close relative whose feelings would be hurt and family ties strained were you to refuse, then it is acceptable to attend. Yet if boycotting him would cause the sin to be abandoned, then boycott him. For example, should a relative invite you and you know there will be something forbidden, and he agrees to remove it, then accept the invitation; but if he insists on keeping the forbidden element, do not go. Merely being present where the sin occurs—even though one detests it inwardly—makes a person a partner in the act, as Allah says: “He has already revealed to you in the Book that when you hear the signs of Allah being denied and ridiculed, do not sit with them until they engage in some other talk; otherwise you would be like them. Surely Allah will gather the hypocrites and the disbelievers together in Hell” (Q 4:140).

This is the ruling on responding to invitations.

The fifth right: blessing the one who sneezes (tashmīt al-ʿāṭis). Among a Muslim’s rights over his brother is that he bless him when he sneezes. So it is stated in the first narration reported by al-Bukhārī and Muslim, and in the second narration transmitted by Muslim: “If he sneezes and praises Allah, then bless him,” thereby linking the blessing to his saying al-ḥamdu lillāh.

Therefore, when a person sneezes, praises Allah, and you hear him, bless him by saying, “May Allah have mercy on you.”