The evidence that one who dies believing in tawhid will definitely enter paradise Sahih Muslim 30 d
Arabic hadith text
حَدَّثَنَا الْقَاسِمُ بْنُ زَكَرِيَّاءَ، حَدَّثَنَا حُسَيْنٌ، عَنْ زَائِدَةَ، عَنْ أَبِي حَصِينٍ، عَنِ الأَسْوَدِ بْنِ هِلاَلٍ، قَالَ سَمِعْتُ مُعَاذًا، يَقُولُ دَعَانِي رَسُولُ اللَّهِ صلى الله عليه وسلم فَأَجَبْتُهُ فَقَالَ " هَلْ تَدْرِي مَا حَقُّ اللَّهِ عَلَى النَّاسِ " . نَحْوَ حَدِيثِهِمْ
Translation
It is narrated on the authority of Aswad b. Hilal that he heard Mu'adh say this
The Messenger of Allah (ﷺ) called, me and I replied to him. He (the Holy Prophet) said: Do you know the right of Allah upon the people? and then followed the hadith (mentioned above).