When the time of the tenth plague approached for the firstborn in every Egyptian family to die, Moses said to Pharaoh, “But against none of the children of Israel shall a dog move its tongue, against man or beast, that you may know that the LORD does make a difference between the Egyptians and Israel” (Exodus 11:7).
Pharaoh and the Egyptians needed to know that the tenth plague was not a mere phenomenon of nature, but the Lord would do a work among them, persuading them finally to let Israel go.
Do not speak against God’s people, but trust in Him to keep you separate from those who are not His.