In verse 15, God clarifies why he gave man powers. At first glance, it only appears to cover what is physical and material, but with God's spiritual revelation and other scriptures, it carries far greater implication.
In the King James Version, the word meaning "tend" or "cultivate" is dress. The Hebrew means "to work at." In 1611, when the King James was translated, the word dress meant "to set in order," but gradually, it was applied to applying decorative details, "to embellish."
Today, when we say that we are going to dress, we include both parts of that definition. We put ourselves in order and embellish how we look.
In modern Bibles, “dress” has been translated "tend" or "cultivate." They have subtle meanings that are slightly different from "dress." Tend means "to pay attention to" or "to serve." For example, “I am going to tend to the dishes.” It means "to apply oneself to the care of" or "to manage the operations of."
Cultivate, which is the best of the three definitions, means "to put through a finishing process," "to foster the growth of," or "to further or encourage." Neither "dress" or "tend" is wrong, but "cultivate" most accurately applies the Hebrew meaning of the original word.
There is the word "keep" as well. We are to "dress and keep." Keep means to "guard," "preserve," "be faithful to," and "maintain."
God has given man powers to carry out the responsibility that has been given into his hands: to have dominion. Man must do the following: Put what has been placed into his hands through a finishing process, watch over it, guard it, protect it, and preserve its beauty.
This was all given to Adam and Eve in the Garden of Eden, a beautiful place. God let them and us know that, as beautiful as the Garden was, it would not stay that way. It was subject to natural law and would degenerate. The Garden would need to be maintained, cultivated, dressed, and kept, requiring a great deal of work. Man was not only to preserve, control, and direct it, but also to strive even to ennoble the Garden of Eden through work.
It begins to become clear that God intends mankind to make more of his environment than he has been given. God has given the powers to do that. We are to understand this not only physically, but more importantly, spiritually.
Here in Genesis, God has shown the fact that a person works, the reason why he works, and the way he works all have a great deal to do with his spiritual development. It is important to note the difference between "salvation" and "development." We are saved by grace. But if there is going to be development from where God begins whenever we first receive His Spirit, then it requires something on our part to enable the fullness of development to take place. That involves work.