A surah’s ending, like its beginning, performs a rhetorical function. It may consolidate wise counsel, reaffirm a command, or emphasize the warning attached to violating what has been taught.
A proclamation that ends by restating the essential instruction or its consequence leaves the intended outcome firmly in mind. By analogy, the final verses of a surah may gather up its preceding discourse or sharpen the impact of its instruction.
Interpretive question: it is not enough to identify the words in the conclusion. One should also ask which purpose from the opening and body of the surah the ending strengthens or completes.