thirst for righteousness, for they will be filled.”
To hunger and thirst for righteousness is to look forward to the promise of new heavens and a new earth (2 Peter 3:13): to long for it, to desire it, to pine for it, to seek it, to prepare for it and to keep praying for it until it arrives. It implies that we are not content with things just the way they are, and we are not satisfied to just let things go along as they always have.
We hate sin, we hate the effects of sin upon this earth, and we mourn the consequences of man’s inhumanity to man and rebellion towards God; but we have hope for a better day, a better life, a better world where Righteousness Himself is living among us. Until such time, we are hungry and thirsty for more of what we have only just begun to taste.