The Institutes of Biblical Law by Rousas John Rushdoony
The Sixth commandment pg. 223
Rousas John Rushdoony said:
The purely personal violations of this law involve any and every abuse of our body which is destructive of our health and in violation of God's will for us...
The personal application includes markings, cuttings, and tattoos of the body, for the body must be used under God’s law, and all such acts are forbidden in the law, whether for morning, as religious marks, or for ornamental or other uses (Lev. 19:28 21:5). Tattooing was practiced religiously to indicate that one adhered to or belonged to a god; it also indicated that a man was a slave, that he belonged to a lord or owner. The believer, as a free man in Christ, indicates Christ’s lordship by obedience, not by servile markings: the body is kept holy and clean unto the Lord. The persistence of a mark of slavery among men is indicative of man’s perversity.
... the sixth commandment, like the first, has a reference to all ten commandments. When the law declares, "Thou shalt have no other gods before me" (Ex. 20:3), it means in part that every violation of any law involves placing ourselves and our will above God's word and is there fore a violation of the first commandment. Similarly, when the law declares, "Thou shalt not kill, " it means that any violation of the first and second 'tables' of the law involves a destruction of our life in relationship to God.