John Chrysostom

By righteousness is here meant universal virtue. But observe the superior power of grace, in that He requires of His disciples who were yet uninstructed to be better than those who were masters under the Old Testament. Thus He does not call the Scribes and Pharisees unrighteous, but speaks of their righteousness. And see how even herein He confirms the Old Testament that He compares it with the New, for the greater and the less are always of the same kind.