All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
One should not rule that an original Kaafir (non-Muslim) has become a Muslim simply because some sources said that he embraced Islam before his death.
Rather, he is ruled to be a non-Muslim as per his principle state. The jurists stated that we have to apply the principle in regard to the original non-Muslim when two people differ in opinion about him becoming a Muslim or not; meaning if one of them says that he died as a Muslim and the other says that he died upon his original faith.
Therefore, if there is no evidence that a dead person who is originally a non-Muslim proving that he has embraced Islam, then the ruling that applies to him is that he is a non-Muslim, as this is his principle state.
If someone claims that he has embraced Islam, then he has to provide evidence. The evidence based on which a person who died as a non-Muslim may be considered as having embraced Islam is the testimony of two men.
An-Nawawi said in his book Rawdhatu At-Taalibeen about the quorum of the testimony in matters that do not involve money and matters that are known to men in general: “The only accepted quorum is the testimony of two men in matters like marriage, taking one’s wife back (after divorce), divorce, emancipation (of a slave), (embracing) Islam and apostasy.” [End of quote]
Allah knows best.