Why does it say "b'Virkas Yesharim Tarum Kares"?
Rashi: The roof of the house will stay elevated and not fall. As long as Malchei Yehudah were Yesharim, their Tefilah kept the Beis ha'Mikdash standing.
R. Yonah #1: When Yesharim succeed in wealth and honor, the country is elevated, for Yesharim draw the hearts of people with their Chachmah. They counsel them with Da'as, for they have good, straight Sechel. When they succeed in wealth and honor, people heed their words.
R. Yonah #2: They elevate the city via their prayers and Brachos, which are accepted - "u'Sefilas Yesharim Retzono" (15:8).
Malbim: Yesharim have Binah. Their nature leans to good, and they go beyond the letter of the law (3). This influences Brachah on the city, which elevates the city. Brachah comes via added influence of Kedushah in the Nefesh of the one who blesses.
How does the mouth of Resha'im destroy?
R. Yonah: Via tale-bearing and arousing quarrels. They elevate Sheker and lower Emes.
Malbim: It is via their curse or Leshon ha'Ra.
