Hisnul Muslim 230

For one you have insulted

اللَّهُمَّ فأَيُّمَا مُؤْمِنٍ سَبَبْتُهُ فَاجْعَلْ ذَلِكَ لَهُ قُرْبةً إلِيْكَ يَوْمَ الْقِيَامَةِ

Allaahumma fa'ayyumaa mu'minin sababtuhu faj'al thaalika lahu qurbatan 'ilayka yawmal-qiyaamati.

O Allah, whomever of the believers I have abused, give him the reward of a sacrificial slaughter for it on the Day of Resurrection.