What is the ruling on attending a party that contains a temporary reprehensible act that will soon disappear, with the possibility of staying away from hearing the reprehensible act and then returning, or attending after it has disappeared?

It is not permissible to attend a gathering where there is a forbidden act (munkar) except for the purpose of denouncing it. If one is unable to change the munkar, then they must leave, otherwise they would be sinful. If the munkar is removed, there is no impediment to attending. However, if the munkar returns, it is obligatory to denounce it, and then to depart if the denouncement is ineffective. This condition applies to gatherings that are originally permissible, such as weddings and Eid celebrations. As for innovative celebrations like Mawlids (celebrations of the Prophet's birthday), it is not permissible to attend them except for the purpose of denouncing, based on the generality of Allah's saying: "And leave those who take their religion as amusement and play and whom the worldly life has deluded" (Quran 6:70), and His saying: "And of the people is he who buys the amusement of speech to mislead [others] from the way of Allah without knowledge and who takes it in ridicule. Those will have a humiliating punishment" (Quran 31:6).