To improve relationships, even with enemies, the Bible recommends hospitality.
يُخْبِرُ ٱلْكِتَابُ ٱلْمُقَدَّسُ أَنَّ ٱلضِّيَافَةَ تُحَسِّنُ ٱلْعَلَاقَاتِ بَيْنَ ٱلنَّاسِ ،‏ حَتَّى بَيْنَ ٱلْأَعْدَاءِ .‏ ‏