the obligation remains; so accept the invitation, for he is a Muslim.

Condition 2: The host’s wealth must be lawful.
If all of his money is illicit—such as someone whose income comes entirely from riba (usury)—then you are not obliged to respond, because his wealth is unlawful. A Muslim should exercise scrupulousness and avoid eating from the property of one whose earnings are entirely haram, although doing so is not itself forbidden. It is not unlawful for you to eat food purchased with ill-gotten gains, for the Prophet ﷺ ate from the food of the Jews of Madinah even though they dealt in usury. Nonetheless, piety dictates steering clear of the wealth of a person whose entire income is haram.

If, however, the host’s wealth is mixed—some lawful, some unlawful through shady trade or forbidden transactions—then there is no harm in accepting his invitation, and you need not be overly scrupulous. In truth, few people nowadays are completely free of tainted earnings: some cheat in business, some engage in usury in certain dealings; even many salaried employees fall short in their duties, arriving late or leaving work early. In proportion to the time they shirk, the salary they collect is haram, for they are contractually bound to work from a set hour to a set hour. Were you to scrutinize people today, you would discover that many have some trace of unlawful income in their wealth.

Condition 3: The gathering must be free of wrongdoing. If you know that the event will involve objectionable acts—hiring singers, providing water pipes, or permitting cigarette smoking—it is not obligatory to attend, unless you are able to eradicate the wrongdoing. In that case you must attend for two reasons: