كتاب الإيمان
1
The Book of Faith
(10)
Chapter: The evidence that one who dies believing in tawhid will definitely enter paradise
(10)
باب مَنْ لَقِيَ اللَّهَ بِالإِيمَانِ وَهُوَ غَيْرُ شَاكٍّ فِيهِ دَخَلَ الْجَنَّةَ وَحَرُمَ عَلَى النَّارِ

It is narrated on the authority of Mu'adh b. Jabal that the Messenger of Allah (ﷺ) said:

Mu'adh, do you know the right of Allah over His bondsmen? He (Mu'adh) said: Allah and His Apostle know best. He (the Messenger of Allah) said: That Allah alone should be worshipped and nothing should be associated with Him. He (the Holy Prophet) said: What right have they (bondsmen) upon Him in case they do it? He (Mu'adh) said: Allah and His Apostle know best. He (the Holy Prophet) said: That He would not punish them.
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ قَالَ ابْنُ الْمُثَنَّى حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي حَصِينٍ، وَالأَشْعَثِ بْنِ سُلَيْمٍ، أَنَّهُمَا سَمِعَا الأَسْوَدَ بْنَ هِلاَلٍ، يُحَدِّثُ عَنْ مُعَاذِ بْنِ جَبَلٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ يَا مُعَاذُ أَتَدْرِي مَا حَقُّ اللَّهِ عَلَى الْعِبَادِ ‏"‏ ‏.‏ قَالَ اللَّهُ وَرَسُولُهُ أَعْلَمُ ‏.‏ قَالَ ‏"‏ أَنْ يُعْبَدَ اللَّهُ وَلاَ يُشْرَكَ بِهِ شَىْءٌ - قَالَ - أَتَدْرِي مَا حَقُّهُمْ عَلَيْهِ إِذَا فَعَلُوا ذَلِكَ ‏"‏ ‏.‏ فَقَالَ اللَّهُ وَرَسُولُهُ أَعْلَمُ ‏.‏ قَالَ ‏"‏ أَنْ لاَ يُعَذِّبَهُمْ ‏"‏ ‏.‏
Reference : Sahih Muslim 30 c
In-book reference : Book 1, Hadith 52
USC-MSA web (English) reference : Book 1, Hadith 48
  (deprecated numbering scheme)