Sahih al-Bukhari #15

ثَلاَثٌ مَنْ كُنَّ فِيهِ وَجَدَ حَلاَوَةَ الإِيمَانِ أَنْ يَكُونَ اللَّهُ وَرَسُولُهُ أَحَبَّ إِلَيْهِ مِمَّا سِوَاهُمَا

The Prophet (ﷺ) said, 'Whoever possesses the following three qualities will have the sweetness of faith: The one to whom Allah and His Messenger become dearer than anything else; who loves a person and he loves him only for Allah's sake; who hates to revert to disbelief as he hates to be thrown into the fire.'