ذِكْرُ الشَّيْءِ الَّذِي إِذَا قَالَهُ الْمَرْءُ لِلْمُسْدِي إِلَيْهِ الْمَعْرُوفَ عِنْدَ عَدَمِ الْقُدْرَةِ عَلَى الْجَزَاءِ يَكُونُ مُبَالِغًا فِي ثَوَابِهِ
the Messenger of Allah ﷺ said, "Whoever some good was done to him, and he says: 'May Allah reward you in goodness' then he has done the most that he can of praise." (Using translation from Tirmidhī 2035)
قَالَ رَسُولُ اللَّهِ ﷺ «مَنْ صُنِعَ إِلَيْهِ مَعْرُوفٌ فَقَالَ لِفَاعِلِهِ جَزَاكَ اللَّهُ خَيْرًا فَقَدْ أَبْلَغَ فِي الثَّنَاءِ»