"A good word is like a tree..." This sets up the comparison between a word and a tree, suggesting that a good word possesses qualities similar to a healthy tree.
"...whose root firmly fixed..." The roots of a tree anchor it to the ground, providing stability and sustenance. This refers to the foundation of a good word. It implies that a good word should be based on truth, honesty, and integrity. It should have a solid basis in reality and not be built on flimsy or misleading claims.
"...and top in the sky..." The top of a tree reaches towards the sky, symbolizing aspiration and growth. This refers to the impact and influence of a good word. A good word should have the power to inspire, uplift, and motivate others. It should aim to create positive change and contribute to a better future.
Overall meaning:
The verse suggests that a good word should be grounded in truth and purpose, while simultaneously aiming for higher ideals and positive impact. Just as a strong tree stands tall and provides benefits to its surroundings, a good word should have a lasting effect and leave a positive mark on the world.