大般涅槃經義記 2.31

2.31

第二如來述讚之中，「善哉」嘆辭。「汝等善修」，出其所嘆。於有為過，此實能治，故佛嘆之。

In the second part, the Tathāgata's affirmation and praise: 'Excellent' is an expression of praise. 'You have cultivated well' states what is praised. Toward the faults of the conditioned, this is indeed able to remedy them; hence the Buddha praises it.