Rashi cites Chazal who place emphasis on the word ,mjf, approximately midnight, which implies either before midnight or after it. Moshe did not specify exactly midnight lest Pharaoh’s astrologers say, “Moshe is a liar.” The simple interpretation of Chazal is that if Moshe is inaccurate by even one minute, this would give Pharaoh’s advisors license to destroy Moshe’s credibility. This is incredible! If all of the firstborn of Egypt were to die as Moshe had predicted, but it happened one minute past the prescribed time, would that have been sufficient cause to deny Moshe’s veracity?
Horav Eliyahu Meir Bloch z.l., derives an invaluable lesson from this Chazal. A Jew must be vigilant not to profane Hashem’s Name, even for a moment. We can not begin to realize the terrible loss created by a momentary chillul Hashem, even if it is immediately rectified. Nevertheless, the damage has been done.
We similarly apply this concept to human beings. A person rushes to do everything possible to remove any taint of suspicion which has been cast upon him, even if after a short while it will be verified that this suspicion was groundless. He does not want to be branded with this taint of suspicion even fleetingly. How much more so must we be sensitive to kavod Shomayim, the honor of Hashem!