Is girls' singing at a school party forbidden (haram), and what is the ruling on saying "O our Lord, rescue us and help us," intending 'Isa (Jesus), peace be upon him, with music playing? Is it permissible to attend the party, and is it obligatory to advise them?

The supplication, "O our master, help us and aid us," is major shirk (polytheism), because it is a supplication to other than Allah for something only Allah can do. It is precisely what the Scriptures were revealed and the Messengers sent to forbid. Allah Almighty says: "And We did not send before you any messenger except that We revealed to him that there is no deity except Me, so worship Me." The Noble Qur'an is full of verses that forbid supplicating to other than Allah, including: "And whoever invokes with Allah another deity for which he has no proof - then his account is only with his Lord. Indeed, the disbelievers will not succeed," and "And do not invoke besides Allah that which neither benefits you nor harms you; for if you did, then indeed you would be among the wrongdoers," and "So do not invoke with Allah another deity, lest you be among those tormented," and "And do not invoke with Allah another deity. There is no deity except Him. Everything will perish except His Face. To Him belongs the judgment, and to Him will you be returned," and "And that the mosques are for Allah, so do not invoke with Allah anyone."

Scholars like Ibn Taymiyyah and Al-Mu'allimi view supplicating to other than Allah, whether deceased or absent, from prophets or righteous people, for help or assistance, as shirk with Allah. And singing accompanied by musical instruments is forbidden by scholarly consensus. One must not attend such celebrations that involve forbidden acts without condemning them, because sitting in a gathering of disobedience without condemning it means approval of the act, and approval of disbelief is disbelief. Allah Almighty says: "And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, then do not sit with them until they enter into another conversation. Indeed, you would then be like them. Indeed, Allah will gather the hypocrites and disbelievers in Hell all together." And counsel must be given, and the danger of this act and the shirk it entails must be clarified.