He may mean either general righteousness, or that particular virtue which is the opposite of covetousness. As He was going on to speak of mercy, He shews before hand of what kind our mercy should be, that it should not be of the gains of plunder or covetousness, hence He ascribes to righteousness that which is peculiar to avarice, namely, to hunger and thirst.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).