Proverbs 23:16

Yea, my reins shall rejoice, when thy lips speak right things.

The word reins means the innermost parts, so the rejoicing is joy felt deep within, not on the surface but in the heart itself. The saying belongs to a chapter of sayings that teach practical moral and religious duties, including sincerity and accepting instruction, while warning against intemperance and other forms of evil. It describes the speaker's deepest feelings rejoicing when the person addressed speaks what is right.

A parent's heart and inward feelings rejoice with deep joy when a child's lips speak what is right, and upright speech is a cause of such parental gladness. Such wise speech is a sign of the wisdom commended in the surrounding verses. Wisdom, given by God, leads a person to speak what is right, and when wisdom so guides a son this brings the deepest joy of heart to a parent or teacher, a joy coming from the innermost parts.

Right speech also brings joy to the Lord, and lips that speak what is right show a wise heart. God wants His people to rejoice when they gather together, and speaking what is right and standing in the light keeps that joy from lust after wrong things and from unseemly excess. The strong drink of ancient times is not to be compared with present poisonous preparations.