What is the ruling on money taken from a foreign woman after an illicit relationship? Must it be returned to her? Is what was spent from it considered a debt? And is boycotting this woman a condition for the husband's repentance in order to regain his wife?

You must hasten to repent to Allah Almighty for fornication by abandoning the sin, regretting it, resolving never to return to it, cutting off ties with the woman, concealing the sin, and striving in righteous deeds.

As for the money you took from the woman: - If it was a pure gift for no forbidden reason, then it is yours, and you are not obliged to return it. - If it was for the purpose of the forbidden relationship, then it is not lawful for you, and you should not return it to her. Rather, spend it on theibilities of Muslims and avenues of charity.