Is a scholarship student who wishes not to return to his home country obligated to repay the scholarship costs to his employer? And is the money spent on him considered a debt upon him?

An ijarah (leasing/hiring) contract is a binding contract, and neither party may unilaterally terminate it unless there is an impediment to fulfilling its obligations.

If it is possible for you to practice your religious rituals in your country, then you must return and complete the contract with the company, or reach a mutually agreeable compensation settlement.

However, if you are unable to practice your religion in your country, this is an excuse that permits you to terminate the contract. In this case, you must return all expenses the company incurred for your training and all wages paid to you, unless you provided services during the training, in which case their value will be deducted, and the remainder returned.