The Commandment against adultery has obvious physical purposes, the primary one being to prevent the birth of illegitimate children. But the Commandment has a far greater application because spiritual adultery is an unfaithfulness to God Himself. The children of God will be born (see Born Again, How and When?) because, if they have been faithful, they have been conceived by The Holy Spirit of God (see Spiritual Conception. Those who choose to be, or become, adulterous to The Father's Spirit become children of another father: "8:44 Ye are of your father the devil, and the lusts of your father ye will do" (John 8:44 KJV).
"This people will rise up and go a whoring after the gods of the strangers of the land ... and will forsake Me"
The carnal-minded ancient Israelites were unfaithful to God, over and over and over (listen also to the Sermon The Divorce and Remarriage of Jesus Christ from our Sermons page). Spiritual adultery was the reason that the adult Israelites of the Exodus, after they became corrupt, were left to die in the desert (see A Journey Without A Destination). It was their children, forty years later, who were given to enter the promised land. But were they any different? No. The LORD Himself prophesied what was coming:
"31:14 And the LORD [see also YHVH, Adonai, Jehovah, LORD and 'The God Of The Old Testament'] said unto Moses [see The Education Of Moses and The Trysting Tent], Behold, thy days approach that thou must die: call Joshua, and present yourselves in the tabernacle of the congregation, that I may give him a charge. And Moses and Joshua went, and presented themselves in the tabernacle of the congregation.
31:15 And the LORD appeared in the tabernacle in a pillar of a cloud: and the pillar of the cloud stood over the door of the tabernacle. 31:16 And the LORD said unto Moses, Behold, thou shalt sleep [see What Happens When You Die?; also Why Did Christ Put Moses To Death?] with thy fathers; and this people will rise up, and go a whoring after the gods of the strangers of the land, whither they go to be among them, and will forsake me, and break my covenant which I have made with them.
31:17 Then my anger shall be kindled against them in that day, and I will forsake them, and I will hide my face from them, and they shall be devoured, and many evils and troubles shall befall them; so that they will say in that day, Are not these evils come upon us, because our God is not among us?
31:18 And I will surely hide my face in that day for all the evils which they shall have wrought, in that they are turned unto other gods.
31:19 Now therefore write ye this song for you, and teach it the children of Israel: put it in their mouths, that this song may be a witness for me against the children of Israel.
31:20 For when I shall have brought them into the land which I sware unto their fathers, that floweth with milk and honey; and they shall have eaten and filled themselves, and waxen fat; then will they turn unto other gods, and serve them, and provoke me, and break my covenant [see Why A New Covenant?]. 31:21 And it shall come to pass, when many evils and troubles are befallen them, that this song shall testify against them as a witness; for it shall not be forgotten out of the mouths of their seed: for I know their imagination which they go about, even now, before I have brought them into the land which I sware.
31:22 Moses therefore wrote this song the same day, and taught it the children of Israel." (Deuteronomy 31:14-22 KJV)
Moses had known the rebelliousness of the people for forty years. Joshua would have the same experience with them for the twenty five years that he was given to lead them after crossing the Jordan.
"31:23 And he gave Joshua the son of Nun a charge, and said, Be strong and of a good courage: for thou shalt bring the children of Israel into the land which I sware unto them: and I will be with thee.
31:24 And it came to pass, when Moses had made an end of writing the words of this law in a book, until they were finished, 31:25 That Moses commanded the Levites, which bare the ark of the covenant of the LORD, saying,
31:26 Take this book of the law, and put it in the side of the ark of the covenant of the LORD your God, that it may be there for a witness against thee.
31:27 For I know thy rebellion, and thy stiff neck: behold, while I am yet alive with you this day, ye have been rebellious against the LORD; and how much more after my death?
31:28 Gather unto me all the elders of your tribes, and your officers, that I may speak these words in their ears, and call heaven and earth to record against them.
31:29 For I know that after my death ye will utterly corrupt yourselves, and turn aside from the way which I have commanded you; and evil will befall you in the latter days; because ye will do evil in the sight of the LORD, to provoke him to anger through the work of your hands.
31:30 And Moses spake in the ears of all the congregation of Israel the words of this song, until they were ended." (Deuteronomy 31:23-30 KJV)
Fact Finder: (a) What happened after King Solomon committed spiritual adultery? (b) What happened after the northern Kingdom of Israel committed spiritual adultery? (c) What happened after the southern Kingdom of Judah committed spiritual adultery?
(a) See Solomon's Compromise and The Division Of Israel
(b) See The Northern Kingdom and The Galilee Captivity
(c) See The Southern Kingdom and Why Babylon?