What is the ruling on working in a place designated for training women in various types of dance as a hobby, and the ruling on earning money from it, and what must be done if this earning is unlawful, especially since the training is conducted with music?

It is not permissible for a Muslim living in Islamic lands to work in places where women dance and display their 'awrah (private parts), as this is haram (forbidden) and known by necessity to be so in the religion. Whoever does this exposes themselves to the wrath and anger of Allah, and assists in spreading corruption. Money earned from training women in nude dancing is haram and must be disposed of through charity in charitable and good causes.

Allah the Almighty said: "Have you not considered how your Lord dealt with 'Aad - [With] Iram - who had lofty pillars, The likes of whom had never been created in [any] land? And [with] Thamud, who carved out rocks in the valley? And [with] Pharaoh, owner of pegs? [All of] whom oppressed in the lands And increased therein the corruption. So your Lord poured upon them a scourge of punishment. Indeed, your Lord is an observer." (Al-Fajr/6-14)