Anas ibn Malik reported: The Messenger of Allah, peace and blessings be upon him, said, “The faith of a servant is not upright until his heart is upright, and his heart is not upright until his tongue is upright. A man will not enter Paradise if his neighbor is not secure from his evil.”
Source: Musnad Aḥmad 12636
Grade: Hasan (fair) according to Al-Albani
عَنْ أَنَسِ بْنِ مَالِكٍ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَا يَسْتَقِيمُ إِيمَانُ عَبْدٍ حَتَّى يَسْتَقِيمَ قَلْبُهُ وَلَا يَسْتَقِيمُ قَلْبُهُ حَتَّى يَسْتَقِيمَ لِسَانُهُ وَلَا يَدْخُلُ رَجُلٌ الْجَنَّةَ لَا يَأْمَنُ جَارُهُ بَوَائِقَهُ
12636 مسند أحمد باقي مسند المكثرين
2554 المحدث الألباني خلاصة حكم المحدث حسن في صحيح الترغيب