The mouth of the righteous speaketh wisdom - Foolish and corrupt conversation cannot come out of their mouth. They are taught of God, and they speak according to the wisdom that is from above.
The mouth of the righteous speaketh wisdom - That is, It is a characteristic of the righteous to speak “wise things;” not to utter folly. His conversation is serious, earnest, true, pure; and his words are faithful, kind, and just. This, as a part of human conduct, is one of the reasons why God will bless him with prosperity and length of days.
And his tongue talketh of judgment - That is, of just or righteous things. See Matthew 12:35.