Several books and opinions of scholars are used as evidence in the decision, including the books of I’anah Taliban, Is’adur Rafiq, Madzahibul Arba’, and al-Fatawa al-Fiqhiyyah al-Kubra. One of the arguments used to decide the problem is taken from the book al-Fatawa al-Fiqhiyyah al-Kubra juz 1 page 199;
اما النساء امام لا ل لهن انه ام

As for a woman who dances in front of a person who is not lawful for her (read: not her muhrim), then it is unlawful.
This opinion or decision —on several social media pages — is still reaping the pros and cons of the law that was issued. Some netizens even argued that this issue is returned to the community, depending on their beliefs. According to some people, there is something more worthy of discussion than the problem of female and female singers and requires an actual legal product.
Apart from such contradictions (differences of opinion regarding the legal context), female singers who appear at the haflatul imtihan event cannot be justified in a civilized manner. Haflatul imtihan, the hallmark of the celebration of pesantren, should remain in line with the breath of the existing pesantren, not to be damaged by performances and traditions that are inappropriate to be held. Wallahu a’lam…
Note: translated by editor from www.duniasantri.co/pesantren-dan-pergeseran-nilai-haflatul-imtihan
