To someone who has done you a favour
To someone who has done you a favour: 1 supplication in Arabic with English translation and sources, from the Fortress of the Muslim (Hisn al-Muslim).
الدعاء لمن صنع إليك معروفا
جَزَاكَ اللَّهُ خَيْراً.
May Allah reward you with good.
Fortress of the Muslim (Hisn al-Muslim), Sa‘id ibn ‘Ali al-Qahtani. MushafPlus translation made from the Arabic, not reviewed by a specialist.