God rest ye merry, gentlemen
Let nothing you dismay
Remember Christ our Savior
Was born on Christmas Day
— "God Rest Ye Merry, Gentlemen"
The first line of this very old (15th century, by some estimates) song has a number of elements that typically throw listeners for a loop; in addition to the ambiguity of the verb rest, there's the swapping out of "you" for the ecclesiastical pronoun "ye" in some versions, as well as inconsistency with regard to where the comma is placed.
Because some texts place the comma before "merry," some readers or listeners interpret the adjective as modifying "gentlemen," leaving rest as a transitive verb with you as its object (for a phrasing similar to "God rest your soul" or "God bless you"). But "god rest you merry" was, at the time the text was written, an established expression of good wishes in its own right:
AUDREY. Do, good William.
WILLIAM. God rest you merry, sir.
— William Shakespeare, Romeo and Juliet
With that interpretation, "gentlemen" becomes an instance of direct address: "be well and happy, Gentlemen."