Muslims are not to judge others to be from the dwellers of Hellfire unless they inform them about Islam

Q 5: A young intellectual Buddhist lady has recently embraced Islam after seven years of extensive research, and she is now performing Da'wah (calling to Islam). Some men and women embraced Islam thanks to her Da'wah. During one of her trips to introduce Islam in a distant area, a Budhist asked her, "How can you, Muslims, be certain that non-Muslims will go to Hellfire, although we in this region have never heard about Islam before? Are our parents going to go to Hellfire? How is it their fault if you, Muslims, have not conveyed the true religion to us?" This lady called us and asked us to provide a satisfactory answer to that man's inquiry, given that he has embraced Islam after this meeting.

A: Muslims should not judge others to be inhabitants of Hellfire, except in one case, if the Qur'an and its interpretation has reached them from the Du'ah (callers to Islam) in the formers' language, as Allah says, ...this Qur’ân has been revealed to me that I may therewith warn you and whomsoever it may reach. (Surah Al-An'am, 6: 19) Allah also says, And We never punish until We have sent a Messenger (to give warning). (Surah Al-Isra', 17: 15) (Part No. 3; Page No. 497) Those whom Da'wah has not reached yet and insist on Kufr (disbelief) are going to go to Hellfire, according to the two previously mentioned Ayahs, and according to the saying of the Prophet (peace be upon him), By Him in whose Hand my soul is, every Jew or Christian of this Ummah (nation) who hears about me and dies unbelieving in me will be of the inhabitants of Hellfire. Related by Muslim in his Sahih (authentic) Book of Hadith. There are many Ayahs and Hadiths which reinforce this meaning.As for those whom Da'wah has not reached in an uncorrupted manner, they are left to the Will of Allah. The most authentic opinion of the scholars about them is that they are tested on the Day of Judgment; those who obey will enter Jannah, while those who disobey will enter Hellfire. This was implied by Al-Hafizh ibn Kathir (may Allah be merciful to him) in his interpretation of Allah's saying, And We never punish until We have sent a Messenger (to give warning). And Ibn Al-Qayyim (may Allah be merciful to him) in his book entitled "Tariq Al-Hijratayn" under the following title "Ranks of legally competent people". You should refer to those books for more information.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions!