Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:3:85 –

And whoever desires other than Islam as religion - never will it be accepted from him, and he, in the Hereafter, will be among the losers.  

The following was revealed regarding those who apostatized and became disbelievers: Whoever desires a religion other than Islam, it shall not be accepted from him and in the Hereafter he shall be among the losers, because he will end up in the Fire, made everlasting for him.
القرآن:٣:٨٥ –

وَمَنْ يَبْتَغِ غَيْرَ الْإِسْلَامِ دِينًا فَلَنْ يُقْبَلَ مِنْهُ وَهُوَ فِي الْآخِرَةِ مِنَ الْخَاسِرِينَ  

{ومن يبتغ غير الإسلام دينا فلن يقبل منه وهو في الآخرة من الخاسرين} لمصيره إلى النار المؤبدة علية.