Mode of action or attribute?

"Yahweh is again reminded [in Ps 86] that he is a good and forgiving (sallaḥ) God. The grammatical construction of the qaṭṭal verbal adjective, a form occurring only in this passage, underscores 'that here a divine attribute is bing described, not merely a mode of action.' [Kedar, 107f.] The enduring aspect of this forgiving element in God's personality is being emphasized."—Hausmann in TDOT 10:262