The evidence that one who dies believing in tawhid will definitely enter paradise Sahih Muslim 28 b
Arabic hadith text
وَحَدَّثَنِي أَحْمَدُ بْنُ إِبْرَاهِيمَ الدَّوْرَقِيُّ، حَدَّثَنَا مُبَشِّرُ بْنُ إِسْمَاعِيلَ، عَنِ الأَوْزَاعِيِّ، عَنْ عُمَيْرِ بْنِ هَانِئٍ، فِي هَذَا الإِسْنَادِ بِمِثْلِهِ غَيْرَ أَنَّهُ قَالَ " أَدْخَلَهُ اللَّهُ الْجَنَّةَ عَلَى مَا كَانَ مِنْ عَمَلٍ " . وَلَمْ يَذْكُرْ " مِنْ أَىِّ أَبْوَابِ الْجَنَّةِ الثَّمَانِيَةِ شَاءَ
Translation
It is narrated on the authority of Umar b. Hani with the same chain of transmitters with the exception of these words
Allah would make him (he who affirms these truths) enter Paradise through one of the eight doors which he would like.