The Literal Commandment
You shall not uncover the nakedness of your father's wife; it is your father's nakedness. (Leviticus 18:8)
The literal commandment is that a person must not "uncover the nakedness" of your father's wife.
"To uncover the nakedness of" is a Biblical idiom for "having sexual relations with".
The scope of this commandment includes one's biological mother as well as a step-mother.
Messiah Says
Messiah implicitly affirmed this commandment when He spoke about the Law:
"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished. Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven. (Matthew 5:17-19)
Pictures of Messiah
Scripture uses the intimate relationship of marriage to picture the special connection between Messiah and His Bride, Israel. Just as the relationship of husband and wife is not to be "adulterated" by bringing anyone else into their physical intimacy so, too, the spiritual relationship between Messiah and His bride is not to be debased by bringing anyone (or anything!) else into that special bond between the two.
How Messiah Fulfilled
Messiah fulfilled this commandment by not uncovering the nakedness of His father's wife.
Traditional Observance
The traditional observance of this commandment is found in its literal sense: not being conjugally intimate with your father's wife.
Other Notes
We are able to fulfill this commandment today and should not uncover the nakedness of our fathers' wives.
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