And whosoever toucheth one that is slain with a sword in the open fields, or a dead body, or a bone of a man, or a grave, shall be unclean seven days. – Numbers 19:16

But all other flying creeping things, which have four feet, shall be an abomination unto you. And for these ye shall be unclean: whosoever toucheth the carcase of them shall be unclean until the even. – Leviticus 11:23-24

For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: How much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, purge your conscience from dead works to serve the living God? – Hebrews 9:13,14

Our fellow men are a terrible source of defilement to us. Did you not notice in the chapter which we read (Numbers 19) that he who touched the dead body of a man was unclean seven days? Now, if you look in Leviticus 11:23,24, you will see that whoever touched the carcass of an unclean beast was only unclean until the evening! Thus a dead man was seven times more defiling than a dead beast! Such is God’s estimate of fallen, unregenerate man—and it is a just one—for wicked men do many things which brute beasts never do. All ungodly men defile us and I am not sure that I may end there. The truth is still wider. I do not care how you pick your company—and you ought to pick it with great care—but even if you associate with none but saints, they will be an occasion of sin to you at some time or other!

There will be something about them, yes, even about their holiness which may cause you to idolize them, or envy them and, in some way or other, cause you to sin. You cannot, as you are a man of unclean lips and dwell among a people of unclean lips, be altogether without uncleanness and, therefore, you will always have need to use the way of cleansing which the Lord has prepared and revealed. Remember that in the type the least touch defiled—if they only picked up a bone, the Israelites were unclean! If they only walked over a grave they were unclean! My Brethren, the best of you can hardly read in the newspaper an account of a crime without some taint clinging to you! You cannot see sin in another without standing in fearful jeopardy of being, in some degree, infected. ~ C.H. Spurgeon

 https://www.blueletterbible.org/comm/spurgeon_charles/sermons/1481.cfm