«هُوَ الْوَاهِبُ أَلْفَ قِنْطَارٍ»
He is the one who gives a thousand qintars.
The definite participial predicate «الواهب» is qualified by «ألف قنطار». If restriction is intended, it concerns giving such an extraordinary amount, not the claim that no other person gives anything at all.
The example establishes an important point: the complete qualified description is what is restricted. The speaker is singling out giving of a certain magnitude, rather than simply all generosity in the abstract.