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
Sahih Muslim 27 a

It is narrated on the authority of Abu Huraira:

We were accompanying the Apostle (ﷺ) in a march (towards Tabuk). He (the narrator) said: The provisions with the people were almost depleted. He (the narrator) said: (And the situation became so critical) that they (the men of the army) decided to slaughter some of their camels. He (the narrator) said: Upon this Umar said: Messenger of Allah, I wish that you should pool together what has been left out of the provisions with the people and then invoke (the blessings of) Allah upon it. He (the narrator) said: He (the Holy Prophet) did it accordingly. He (the narrator) said: The one who had wheat in his possession came there with wheat. He who had dates with him came there with dates. And Mujahid said: He who possessed stones of dates came there with stones. I (the narrator) said: What did they do with the date-stones. They said: They (the people) sucked them and then drank water over them. He (the narrator said): He (the Holy Prophet) invoked the blessings (of Allah) upon them (provisions). He (the narrator) said: (And there was such a miraculous increase in the stocks) that the people replenished their provisions fully. He (the narrator) said: At that time he (the Holy Prophet) said: I bear testimony to the fact that there is no god but Allah, and I am His messenger. The bondsman who would meet Allah without entertaining any doubt about these (two fundamentals) would enter heaven.
حَدَّثَنَا أَبُو بَكْرِ بْنُ النَّضْرِ بْنِ أَبِي النَّضْرِ، قَالَ حَدَّثَنِي أَبُو النَّضْرِ، هَاشِمُ بْنُ الْقَاسِمِ حَدَّثَنَا عُبَيْدُ اللَّهِ الأَشْجَعِيُّ، عَنْ مَالِكِ بْنِ مِغْوَلٍ، عَنْ طَلْحَةَ بْنِ مُصَرِّفٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم فِي مَسِيرٍ - قَالَ - فَنَفِدَتْ أَزْوَادُ الْقَوْمِ قَالَ حَتَّى هَمَّ بِنَحْرِ بَعْضِ حَمَائِلِهِمْ - قَالَ - فَقَالَ عُمَرُ يَا رَسُولَ اللَّهِ لَوْ جَمَعْتَ مَا بَقِيَ مِنْ أَزْوَادِ الْقَوْمِ فَدَعَوْتَ اللَّهَ عَلَيْهَا ‏.‏ قَالَ فَفَعَلَ - قَالَ - فَجَاءَ ذُو الْبُرِّ بِبُرِّهِ وَذُو التَّمْرِ بِتَمْرِهِ - قَالَ وَقَالَ مُجَاهِدٌ وَذُو النَّوَاةِ بِنَوَاهُ - قُلْتُ وَمَا كَانُوا يَصْنَعُونَ بِالنَّوَى قَالَ كَانُوا يَمُصُّونَهُ وَيَشْرَبُونَ عَلَيْهِ الْمَاءَ ‏.‏ قَالَ فَدَعَا عَلَيْهَا - قَالَ - حَتَّى مَلأَ الْقَوْمُ أَزْوِدَتَهُمْ - قَالَ - فَقَالَ عِنْدَ ذَلِكَ ‏ "‏ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنِّي رَسُولُ اللَّهِ لاَ يَلْقَى اللَّهَ بِهِمَا عَبْدٌ غَيْرَ شَاكٍّ فِيهِمَا إِلاَّ دَخَلَ الْجَنَّةَ ‏"‏ ‏.‏
Reference : Sahih Muslim 27a
In-book reference : Book 1, Hadith 45
USC-MSA web (English) reference : Book 1, Hadith 41
  (deprecated numbering scheme)