In the poem "On Children" by Khalil Gibran, the narrator states that children's souls live "in the house of tomorrow, For which you [parents] cannot visit even in your dreams." What is an interpretation of these words? Give a specific explanation.

In order to get a better understanding of those particular lines, I recommend looking at the previous few lines that lead into them.  

You may give them your love but not your thoughts, For they have their own thoughts.You may house their bodies but not their souls,For their souls dwell in the house of tomorrow, which you cannot visit, not even in your dreams.

The poem's narrator is speaking to parents about their children, and the narrator bluntly tells parents that they are allowed to give children their love but not their thoughts. This means that parents should not force their kids to have the same opinions, likes, dislikes, and so on as the parents do. Children are people, too. They have their own thoughts, wishes, desires, and opinions. Those five lines of the poem really stress the idea that each child is a unique individual, and parents shouldn't try to force a mold on them.  
If a reader considers the five lines that are listed above, the first line tells parents what they cannot do, and the second line is the reason why. Line three again tells parents what they cannot do, and lines four and five contain the reason. Parents cannot contain the soul or spirit of their children, because that part of the child is the part that dreams of his or her own future. That future is one that does not involve the parents. It is a future that the parents cannot even fathom, and that is why parents cannot visit it in their dreams.