Supplication for someone you have spoken ill to
اَللّٰہُمَّ فَاَیُّمَا مُؤْمِنٍ سَبَبْتُہٗ فَاجْعَلْ ذٰلِکَ لَہٗ قُرْبَۃً إِلَیْکَ یَوْمَ الْقِیٰمَۃِ
O Allah, to any believer whom I have insulted, let that be cause to draw him near to You on the Day of Resurrection.
References
[Sahih Bukhari - 6361]
Notes
According to human requirements, if the Prophet (peace and blessings of Allaah be upon him) was angry with someone and said obscene words about him, then he would pray for him.
