A Christian might have offended someone and needs to apologize. Or he might have made a mistake and needs to admit it. What if someone commits a serious sin?
وَرُبَّمَا أَسَاءَ مَسِيحِيٌّ إِلَى شَخْصٍ وَعَلَيْهِ أَنْ يَعْتَذِرَ .‏