Sahih Muslim 30
Sahih Muslim · Book 1: The Book of Faith · The evidence that one who dies believing in tawhid will definitely enter paradise
It is narrated on the authority of Aswad b. Hilal that he heard Mu'adh say this:
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 .
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).