And even yet the difficulties in Moses' way were not removed wholly. The Egyptian magicians had stationed two golden dogs at Joseph's coffin, to keep watch, and they barked vehemently if anyone ventured close to it. The noise they made was so loud it could be heard throughout the land, from end to end, a distance equal to a forty day's journey. When Moses came near the coffin, the dogs emitted their warning sound, but he silenced them at once with words, "Come, ye people, and behold the miracle!
The real, live dogs did not bark, and these counterfeit dogs produced by magic attempt it!" What he said about real, live dogs and their refraining from barking had reference to the fact that the dogs of the Egyptians did not move their tongues against any of the children of Israel, through they had barked all the time the people were engaged in burying the bodies of their smitten first-born. As a reward God gave the Israelites the law, to cast to the dogs the flesh they themselves are forbidden to eat, for the Lord withholds due recompense from none of His creatures.
Indeed, the dogs received a double reward, for their excrements are used in tanning the hides from which the Torah scrolls are made, as well as the Mezuzot and the phylacteries.