The voice. A voice. This is. second "voice": the voice of Jehovah.
is grass. Figure of speech Metaphor, by which the assertion is boldly made that one thing i. another (i.e. represents it). It differs from the Figure of speech Simile in the next clause, which asserts that one thing only resembles another.
goodliness. grace, or loveliness.
is as. Figure of speech Simile.