Psalm 89:16 (KJV) In thy name shall they rejoice all the day: and in thy righteousness shall they be exalted. 

Who are “they” who rejoice in the Name of the LORD all the day? They are the blessed ones who walk in the light of His countenance – Psalm 89:15 (KJV) Blessed is the people that know the joyful sound: they shall walk, O LORD, in the light of thy countenance. 

Knowledge of the LORD and life with Him brings great joy to the soul. They have experienced the LORD’s protection, for example, delivering them from sin and the temptation to sin – Psalm 89:18 (KJV) For the LORD is our defence; and the Holy One of Israel is our king. 

They have learned to walk in righteousness with the LORD, making right with Him and walking according to His commandments. Amen.