Praise be to Allah the Lord of the Worlds.
It is forbidden to take part in starting what is called a casino or to work there, because it is a place where major sins, which Allah has forbidden, are committed, such as gambling, in addition to spreading vice and corruption on earth. Therefore, it is forbidden to start a casino, work in it or contribute in that in any form, because doing so is helping in sin and rancor.
Every Muslim knows that Allah the Almighty has forbidden gambling. He the Exalted says, "O ye who believe! Intoxicants and gambling, (dedication of) stones, and (divination by) arrows, are an abomination,- of Satan’s handwork: eschew such (abomination), that ye may prosper."{Al-Ma`idah, 90}. He the Almighty has prohibited spreading corruption on the earth, which is embodied, here, in opening a casino. Moreover, opening such a place in a Muslim country is doing mischief on the earth. Allah says, "Those who love (to see) scandal published broadcast among the Believers, will have a grievous Penalty in this life and in the Hereafter: God knows, and ye know not."{An-Nur, 19}. He also says, " and do no mischief on the earth after it has been set in order: that will be best for you, if ye have Faith.."{Al-`Araaf, 85}.
Muslims should ignore those who claim that opening a casino will revive the economy and promote the well-being of society. On the contrary, it will destroy Allah`s blessings and incur His wrath, in addition to the fact that it involves eating up people`s wealth unjustly. Allah the Almighty says, "And do not eat up your property among yourselves for vanities,"{Al-Baqarah, 188}. In addition, whatever money a person earns by working in a casino or because of it is ill-gotten. Thus, a person isn`t allowed to spend such money on himself or his family.
A Muslim should make a living through lawful means, as indicated by the Hadith in whichAbu Hurairah (May Allah be pleased with him) said:
The Messenger of Allah (PBUH) said, "O people! Allah is Pure and, therefore, accepts only that which is pure. Allah has commanded the believers as He has commanded His Messengers by saying: 'O Messengers! Eat of the good things, and do good deeds.' (23:51) And He said: 'O you who believe (in the Oneness of Allah - Islamic Monotheism)! Eat of the lawful things that We have provided you..."' (2:172). Then he (PBUH) made a mention of the person who travels for a long period of time, his hair are dishevelled and covered with dust. He lifts his hand towards the sky and thus makes the supplication: 'My Rubb! My Rubb!' But his food is unlawful, his drink is unlawful, his clothes are unlawful and his nourishment is unlawful, how can, then his supplication be accepted?" [Muslim].
In conclusion, helping others in opening such a casino or promoting it in any form is prohibited by Sharia, because Allah the Almighty says, "but help ye not one another in sin and rancour: fear Allah. for Allah is strict in punishment."{Al-Mai`dah, 2}. And Allah the Almighty knows best.