Charles Ellicott Commentary Numbers 19:11

"He that toucheth the dead body of any man shall be unclean seven days:" — Numbers 19:11 (ASV)

He that toucheth the dead body ... — The defilement caused by touching the dead body of a beast lasted only until the evening (Leviticus 11:24). The death of man was the wages of sin; and hence contact with the dead body of a man was attended by ceremonial defilement of longer duration.