Not graded
Hisn al-Muslim (Fortress of the Muslim) 198
((جَزَاكَ اللَّهُ خَيْراً)).
(If someone does you a favour and you say: (May Allah reward you with goodness.) then you have indeed excelled in praising him.)
Cited in Hisn al-Muslim (Fortress of the Muslim) (No. 198).