قَالَ النَّبِيُّ صلى الله عليه وسلم: ((اللَّهُمَّ فَأَيُّمَا مُؤْمِنٍ سَبَبْتُهُ فَاجْعَلْ ذَلِكَ لَهُ قُرْبَةً إِلَيْكَ يَوْمَ الْقِيَامَةِ)).
(O Allah, to any believer whom I have insulted, let that be cause to draw him near to You on the Day of Resurrection.)
Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 11/171, Muslim 4/2007. The wording in Muslim's report is: 'make it a purification for him and a source of mercy.