Abu'd-Darda' reported that the Prophet, may Allah bless him and grant him peace, said, "Shall I tell you a degree better than prayer, fasting and sadaqa?" "Yes," they replied. He went to say, Improving a state of friendship. Causing discord in a state of friendship is what shaves things away."  

عَنِ النَّبِيِّ ﷺ قَالَ أَلاَ أُنَبِّئُكُمْ بِدَرَجَةٍ أَفْضَلَ مِنَ الصَّلاَةِ وَالصِّيَامِ وَالصَّدَقَةِ؟ قَالُوا بَلَى قَالَ صَلاَحُ ذَاتِ الْبَيْنِ وَفَسَادُ ذَاتِ الْبَيْنِ هِيَ الْحَالِقَةُ  

"Fear Allah and put things right between you," (8:1), Ibn 'Abbas said, "This is an injunction from Allah to the believers to fear Allah and to put things right between them."  

وَأَنْ يُصْلِحُوا ذَاتَ بَيْنِهِمْ