The words "day" and "hour" form a merism of time that refers to any time, and the words "expect" and "know" have similar meanings, so the two phrases here are parallel to emphasize that the coming of the lord will be a total surprise to the servant. However, the phrases should not be combined unless your language has no different words for "know" and "expect" or "day" and "hour." Alternate translation: "at a time when the servant is not expecting him" (See: [[rc://en/ta/man/jit/figs-merism]] and [[rc://en/ta/man/jit/figs-parallelism]])
Possible meanings are 1) this is an exaggeration for the master dealing out harsh punishment toward the slave, or 2) this describes the manner in which the servant will be executed and buried as punishment. (See: [[rc://en/ta/man/jit/figs-hyperbole]])