Charles Spurgeon Commentary Numbers 19:15-16

"And every open vessel, which hath no covering bound upon it, is unclean. And whosoever in the open field toucheth one that is slain with a sword, or a dead body, or a bone of a man, or a grave, shall be unclean seven days." — Numbers 19:15-16 (ASV)

This law was indeed a yoke of bondage which our fathers were not able to bear. It was meant to teach us how easily we can be defiled. Anywhere they went, these people might touch a bone or touch a grave, and then they were defiled; and you and I, however carefully we watch, will find ourselves touching some of the dead works of sin, and becoming defiled. It is a happy circumstance for us that there is the means of purification always at hand; we may always go to the precious blood of Jesus, and may once again be washed clean, and be made fit to go up to the house of the Lord.