My son, if your heart is wise,my heart too will be glad. My inmost being will exult when your lips speak what is right. —Proverbs 23:15-16
Here is a model set forth whereby a sons might gladden the heart of his father, and lend toward the exultation of the father's inmost being. It is set forth as the desire of the father, not as a command like the commandment that a son should honor his father, which is his duty and most assuredly binds him. It is expressed as a desire for the following reasons. First so that the son might recognize those things which his father delights in. Second that the son might also learn to delight in them. Third that the son might be pleased to do those things that his father delights in.
It is the father who divulges to his son what gladdens his own heart. This may not always be done in the most straight forward and recognizable way, so that at times it might be difficult to understand whether a certain task or action brings the father gladness and exultation. Surely the father who seeks to instruct his son will also labor to make known to his son what delights and pleases him, just as the father of this proverbs is doing. To this information a son should ever keep a keen ear, so that at the slightest hint of his fathers approval or happiness, he might take note and be sure to maintain the observance of whatever action or task brought joy to his father.
The commandment of the Law of God which binds all sons regardless of age is:
Honor your father and your mother, that your days may be long in the land that the Lord your God is giving you. —Exodus 20:12
By recognizing what brings gladness and exultation to his father, the son might better learn how to honor his father. In doing this, he is also learning what a father ought to delight in. Part of the instruction that fathers are to impart unto their son(s) is the desire to find an excellent wife (Prov 12:4). The training and equipping of the son is so that he might be a dominion taking, nation building, kingdom advancer, for the Lord Jesus Christ. Part of his duties in regards to these responsibilities is to raise up children of his own who he might instruct in the fear of the Lord. This shows that the son must be recognizing those things which his father delights in so that he knows what he ought to delight in from his own children.
Two things are expressly set forth as gladdening the heart and exulting the inmost being of the father. First, a heart that is wise. By a wise heart is it meant, first, a heart that fears the Lord, walks in his ways, loves him, and serves him (Deut 10:12). Secondly, it is a heart that is kept with all vigilance (Prov 4:23); the son is never to lax his dependency upon God to search and examine his heart. He must ever humble himself before the Lord and see if there be any wicked way in him. He must constantly walk in the ways of the Lord as his father has instructed him, fearing the judgement for disobedience, and trusting by faith that the grace of God is sufficient to save him.
The second thing that exults the inmost being of the father is when the lips of his son speak what is right. Being placed second, this demonstrates that without a wise (redeemed) heart, there is no good speech that can be uttered from the son's mouth, for from the heart flow the springs of life (Prov 4:23; John 7:38). Thus, it is a redeemed son who can fulfill the desires of his father. No unregenerate son can exult the inmost being of his father to such levels as set forth in this passage.
The speech which come forth from the son's mouth will be the same that his mother instructed him to open his mouth for:
Open your mouth for the mute, for the rights of all who are destitute. Open your mouth, judge righteously, defend the rights of the poor and needy. —Proverbs 31:8-9
Thus his wise heart (redeemed state) is not for him to squander, but is a tool for the advancement of Christ's kingdom. It is to assist the destitute, declare justice and righteousness, and defend the rights of the poor and needy. In doing these things he will bring gladness and exultation to his father.