I asked about accepting a gift from an apostate and it has been answered, but what if the case has not reached the judge in order to declare him an apostate and I rebuked that person but he refused to listen, can a gift from him be accepted? Secondly, if I lend that person money after his apostasy, can I accept the money if he pays it back? Meaning, is it haram to give a loan to an apostate, and is it haram to accept it if he pays it back?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

Apostasy is a very serious matter, and declaring a Muslim individual an apostate is a serious verdict entailing many legal implications regarding his life and wealth. It is not a matter that should be discussed by lay people; only well-versed scholars should address this matter. Please, refer to fatwa 14489.

Assuming that a particular Muslim individual is declared an apostate, the question remains as to whether apostasy entails limiting the apostate’s legal capacity, denying him the right to freely dispose of his wealth, regardless of whether or not a ruler or judge issued a ruling on that. Az-Zarkashi said, “Should limiting the apostate's legal capacity be based on a ruling issued by the Islamic judge, or should it become effective as soon as he apostatized (even without an official verdict)? Abu Haamid cited both opinions in Al-Jaami’ (book).” [Al-Manthoor]

There are many details regarding the apostate’s wealth and his legal capacity and right to dispose of his wealth freely as well as the permissibility of engaging in financial transactions with him (sales, gifts, etc.).

As long as the apostate is living in a time and place where the Islamic rulings on apostasy are not implemented and there is no religious authority that can impose legal hajr (restriction of legal capacity) on the apostate and deny him the right to dispose of his wealth freely, then there is no point or real benefit in refraining from engaging in financial interactions with the apostate. Hence, you may accept his gift, loan him money, and accept it if he pays it back.

Allaah knows best.