IQAMA - How to get passport from employer

The situation you have described is explicit violation of the labour law. My 2 cents are to go to labour court.

If the employee was hired from his native country (by the same employer), he'll get all the pending dues followed by a deportation to his country. On the other hand, if he had given Naqal Kafala to this employer, the court will force him to relase him to any other sponsor/company.

(The above however is often time-taking and pains-giving. But at least there is a possibility of redemption.)

Like TheLegendLeads said or he can try & reach a (middle) solution with his employer.
Trying to reason with him to let him get transferred to another employer even if it means not getting all his dues as the labour court takes a really long time (forcing you to settle in the end anyways) & it's bias.
If he knows any of his employer's relatives (even his employer's Imam in the mosque that he goes to) etc he can talk to them (with reason even begging for their help & not anger etc) to put some pressure you know.
Saudis most of the time care about their "reputation" to always look righteous etc.

@ITPro.

Of course litigation must be done only when everything else has already been in vain.