Psalm 37:30-31

30"The mouth of the righteous speaks wisdom, and his tongue talks of justice."
31"The law of his God is in his heart; None of his steps shall slide."

Speaks = murmur in pleasure, to ponder, talk, utter
Talks = arrange, teach, tell
Justice = verdict, divine law, measure
Slide = waver, slip

This is a simple statement with a deep meaning.  It states matter of factly that
the righteous will speak wisdom.  He will murmur in pleasure about the things
of God.

 Deuteronomy 6:7 ^"You shall teach them diligently to your children and shall talk of them when you sit in your house, when you walk by the way, when you lie down, and when you rise up."

He has pondered on the Word of God and taken it to heart. 

He does not waste time on worldly wisdom or idle words.  We should hope to have
God's law hidden deep in our hearts so that when we speak, what we say
coincides with His Word.  If we stand on His Word our path will have no
stumbling blocks to trip us.