An employer cancelled visa and refuses to return passport

Assalamu alaikum, sir.

My employer is a local Emirati and he hired me as a cashier in a grocery store. He did not give me a contract on the first day, and when he applied for a visa for me, he did not ask me.

He gave me his house visa as a servant. After 5 days, he canceled my work approval, and now my status shows that it was canceled before entry.

I asked for my passport, but he is not agreeing to give it to me along with the cancellation paper.

Now, he is saying that I have to go back to my country.

Please give me some advice on what I should do!