Jamieson, Fausset and Brown on Exodus 11:7

7. against any of the children of Israel shall not a dog move his tongue--No town or village in Egypt or in the East generally is free from the nuisance of dogs, who prowl about the streets and make the most hideous noise at any passers-by at night. What an emphatic significance does the knowledge of this circumstance give to this fact in the sacred record, that on the awful night that was coming, when the air should be rent with the piercing shrieks of mourners, so great and universal would be the panic inspired by the hand of God, that not a dog would move his tongue against the children of Israel!