Sahih al-Bukhari 44
Narrated Anas:
The Prophet (ﷺ) said, "Whoever said "None has the right to be worshipped 
     but Allah and has in his heart good (faith) equal to the weight of a 
     barley grain will be taken out of Hell. And whoever said: "None has 
     the right to be worshipped but Allah and has in his heart good (faith)
     equal to the weight of a wheat grain will be taken out of Hell. And 
     whoever said, "None has the right to be worshipped but Allah and has 
     in his heart good (faith) equal to the weight of an atom will be taken
     out of Hell."
حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا هِشَامٌ، قَالَ حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ يَخْرُجُ مِنَ النَّارِ مَنْ قَالَ لاَ إِلَهَ إِلاَّ اللَّهُ، وَفِي قَلْبِهِ وَزْنُ شَعِيرَةٍ مِنْ خَيْرٍ، وَيَخْرُجُ مِنَ النَّارِ مَنْ قَالَ لاَ إِلَهَ إِلاَّ اللَّهُ، وَفِي قَلْبِهِ وَزْنُ بُرَّةٍ مِنْ خَيْرٍ، وَيَخْرُجُ مِنَ النَّارِ مَنْ قَالَ لاَ إِلَهَ إِلاَّ اللَّهُ، وَفِي قَلْبِهِ وَزْنُ ذَرَّةٍ مِنْ خَيْرٍ ‏"‏‏.‏ قَالَ أَبُو عَبْدِ اللَّهِ قَالَ أَبَانُ حَدَّثَنَا قَتَادَةُ حَدَّثَنَا أَنَسٌ عَنِ النَّبِيِّ صلى الله عليه وسلم ‏"‏ مِنْ إِيمَانٍ ‏"‏‏.‏ مَكَانَ ‏"‏ مِنْ خَيْرٍ ‏"‏‏.‏