Sahih al-Bukhari 21
Narrated Anas:
The Prophet (ﷺ) said, "Whoever possesses the following three qualities 
     will taste the sweetness of faith:


     1. The one to whom Allah and His Apostle become dearer than anything 
     else.


     2. Who loves a person and he loves him only for Allah's sake.


     3. Who hates to revert to disbelief (Atheism) after Allah has brought 
     (saved) him out from it, as he hates to be thrown in fire."
حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ ثَلاَثٌ مَنْ كُنَّ فِيهِ وَجَدَ حَلاَوَةَ الإِيمَانِ مَنْ كَانَ اللَّهُ وَرَسُولُهُ أَحَبَّ إِلَيْهِ مِمَّا سِوَاهُمَا، وَمَنْ أَحَبَّ عَبْدًا لاَ يُحِبُّهُ إِلاَّ لِلَّهِ، وَمَنْ يَكْرَهُ أَنْ يَعُودَ فِي الْكُفْرِ بَعْدَ إِذْ أَنْقَذَهُ اللَّهُ، كَمَا يَكْرَهُ أَنْ يُلْقَى فِي النَّارِ ‏"‏‏.‏