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."  

عَنِ النَّبِيِّ ﷺ 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 ﷺ مِنْ إِيمَانٍ مَكَانَ مِنْ خَيْرٍ  

Once a Jew said to me, "O the chief of believers! There is a verse in your Holy Book Which is read by all of you (Muslims), and had it been revealed to us, we would have taken that day (on which it was revealed as a day of celebration." 'Umar bin Al-Khattab asked, "Which is that verse?" The Jew replied, "This day I have perfected your religion For you, completed My favor upon you, And have chosen for you Islam as your religion." (5:3) 'Umar replied,"No doubt, we know when and where this verse was revealed to the Prophet. It was Friday and the Prophet ﷺ was standing at 'Arafat (i.e. the Day of Hajj)"  

لَهُ يَا أَمِيرَ الْمُؤْمِنِينَ آيَةٌ فِي كِتَابِكُمْ تَقْرَءُونَهَا لَوْ عَلَيْنَا مَعْشَرَ الْيَهُودِ نَزَلَتْ لاَتَّخَذْنَا ذَلِكَ الْيَوْمَ عِيدًا قَالَ أَىُّ آيَةٍ قَالَ {الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الإِسْلاَمَ دِينًا} قَالَ عُمَرُ قَدْ عَرَفْنَا ذَلِكَ الْيَوْمَ وَالْمَكَانَ الَّذِي نَزَلَتْ فِيهِ عَلَى النَّبِيِّ ﷺ وَهُوَ قَائِمٌ بِعَرَفَةَ يَوْمَ جُمُعَةٍ