Speaketh constantly - His testimony abides evermore who repeats simply what he has heard, whether from the lips of men or from the voice within, in contrast with “the false witness.”
SDA Bible Commentary (limited)
Volume 1-7
28. The man that heareth. The meaning of this clause is uncertain. Some interpret it as observing that the word of “the man that heareth” stands unchallenged continually because his ear is quick to hear the commands of God and the counsel of man. The LXX renders the clause “an obedient man will speak cautiously.” By contrast the word of a liar perishes when it meets truth (see chs.6:19; 19:5, 9).