KJV:
Mercy and truth preserve the king: and his throne is upholden by mercy.
NASB:
Loyalty and truth preserve the king, And he upholds his throne by righteousness.
KJV:
Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even for ever. The zeal of the LORD of hosts will perform this.
NASB:
There will be no end to the increase of His government or of peace, On the throne of David and over his kingdom, To establish it and to uphold it with justice and righteousness From then on and forevermore. The zeal of the LORD of hosts will accomplish this.