The verse begins with the root system of the joyful man and then focuses on the fruit. "He shall be like a tree planted..."
Let me digress for just a moment. I've been reviewing my Hebrew (it's been almost 20 years, so thank you for grace :) and have rediscovered some of the nuances of verb tenses and voices. Don't get nervous - just bear with me because this is crucial. The QAL is the basic verb tense in Hebrew comprising about 75% of all the verbs. Verbs have tenses (past, present, future - there's more but we will stick to the basics) and also have voices (active or passive - generally). The voice of the verb indicates whether the subject of the verb (ex. I ran down the street. I is the subject and ran is the verb.) is providing the action or if the subject is being acted upon by someone or something else. If a verb is passive it indicates the subject is receiving the action indicated (ex. I was hit by the ball when Chuck threw it to me.) In English we use "helping verbs" to show the voice but in many other languages it is Incorporated into the main verb.
Everybody okay? Here's why that matters. In the phrase, "and he shall be like a tree planted", "he" is the subject (the blessed - joyful - free man) and "planted" is the verb (QAL particple passive voice). Basically it means that being "planted" is a simple and continued action received by the blessed man.
In English what that means is that the tree did not plant itself, the tree did not choose where it was going to be planted or transplanted. It means that the tree was acted upon by an outside power to put the tree in its rightful and good place.
The tree was deliberately planted by the water by Someone who was determined that it should bear fruit.
And so were you!
Planted where? By rivers of water.
When I was in Israel a few years ago I was struck by the vegetation found in En Gedi. En Gedi and vegetation is practically an oxymoron. En Gedi is in the middle of the desert very close to the Dead Sea and Mt. Masada. Trust me when I say nothing grows there. Except in En Gedi. There are natural springs which are cool, refreshing, crystal clear and life giving. En Gedi is home to animals, birds, flowers and trees. For miles around all the terrain is rough hewn mountains, a life-less sea and shimmering sand. Then you come to En Gedi and its beauty can take your breath away.
Our lives in Christ are much like the En Gedi oasis. We are surrounded by the desert of the World and it is life-less indeed. Christ deliberately (trans)planted us in His own En Gedi, Himself, and waters us there with His Word (Eph. 5:26) and His Spirit (John 7:35).
So, what should we believe based on what we've just studied?
At least this: The LORD God Almighty took you out of the desert of the world and transplanted you by His Son and the Power of His Spirit into Himself. In Christ, you are watered with the Word and the Spirit!
Are you starting to see why this man is joyful - happy - free?
What is God teaching you as we study? What have you learned from your muttering about God's law? Is your heart delighting more in the LORD?