Seems like a good one to touch on.
I'm sure there could have been room in there somewhere if he wanted it. Why not?
Note: This answer comes from the perspective of the Old Testament alone, since the question was in regard to the Ten Commandments and gives no indication that it's seeking a "Christian" perspective, but does give indication that it's seeking a historical perspective (since it references the Ten Commandments).
History of the ten Commandments
Why is rape not included among the these commandments? Because there are many things (including homosexuality, having sex with your fathers wife, not wearing clothes made of both wool and cotton, etc.) that are not in them.
The Ten Commandments were originally written on stone tablets after Moses ascended Mount Sinai. Their purpose was to provide a set of basic, simple laws that would hold the nation of Israel over until they got the full Levitical law.
The Levitical law was not given until the book of Leviticus, after the Ten Commandments had been given. These commandments were not meant to be all-encompassing, but simply meant to give them the top-ten basic laws that God wanted the Israelites to obey until they could get the complete Law.
It is important to note that "rape" during those days was not a crime against a woman, but rather a crime against the head of the household (History of Rape).
To understand how rape plays out in the Old Testament, it is important to understand adultery. Adultery was a sin that had the death-penalty associated with it.
However, if the man were to rape another man's wife, only the man would die, since he is the one that committed the act of adultery.
Note that in Old Testament times, betrothal came after the marriage price had been paid. The groom and the bride at that point were effectively married, although there was a waiting period before they could live together.
Now, if a man rapes a woman who is not pledged to be married, then he has not committed adultery and did not deserve death. Instead, he was forced to pay the marriage price, taking the girl/woman as his wife.
What these laws are showing is that rape is not "non-consensual" sex as we think of it today. It's actually a crime against the man who "owns" the woman (for lack of a better term). The crime committed in the case of a betrothed or married girl is the crime of adultery. The crime committed in the case of a non-betrothed, unwed girl is the crime of not paying for something that you've taken.
The punishment for rape back then was the same as the punishment for either adultery or stealing, based on the marital status of the girl.
This also means... there is nothing in the Old Testament saying that non-consensual sex with your wife is wrong.
Rape as Adultery/Theft
With the definition above, we see that rape carried the punishment of either adultery or theft, based on the marital status of the girl/woman. With that in mind, the laws of adultery and stealing were in the Ten Commandments:
If we compare these laws established in the Ten Commandments with the rules established in Deuteronomy, we see that rape was considered either stealing or adultery.
Because of this, the root law that is being violated is actually covered in the these commands.
Rape, from the Old Testament perspective, is either considered adultery or thievery (based on the marital status of the woman). Those two root laws are specifically mentioned in the Ten Commandments. Therefore, the two laws that might be broken from a given rape are actually written there.
Not every sinful act is spelled out in the ten commandments, but every possible sinful act does fall under one or more of the umbrellas. Rape is adultery as well as theft and envy and does not honor the Lord. That's at least four "counts". How much does one need to know that it's wrong?
In the NT we find the ten commandments expounded to include thoughts about the action and heart attitudes as well as the spelled out actions. In short, not having the act of rape spelled out in a commandment is not an oversight, the topic is well covered. I have never heard it alleged that Christianity allowed rape based on it not being the 11th commandment.
The Bible does address the issue of rape. As expected, when the Bible mentions the crime of rape, it is depicted as a gross violation of God’s design for the treatment of the human body (Genesis 34). The Bible condemns rape whenever it is mentioned. For example, there is a particular passage in the laws given to the nation of Israel before entering the Promised Land under Joshua’s leadership. This passage (Deuteronomy 22:13-29) spoke directly against forcing a woman into a sexual encounter against her will, or what we know today as rape. This command was meant to protect women and to protect the nation of Israel from committing sinful actions.
Deuteronomy 22:25-27 mentioned the punishment the Mosaic Law commanded for a man who raped a woman. The man was to be killed by stoning while the woman was considered innocent. Though the Mosaic Law was for the nation of Israel during the time of Moses, the principle is clear that rape was sinful in the eyes of God and led to the most extreme punishment possible—death for the rapist.
There are some difficult passages in the Old Testament, however, in relation to this issue. Critics of the Bible are quick to point to Numbers 31 (and other similar passages) in which the Israelites were allowed to take female captives from nations they conquered. Critics make the accusation that this is an example of the Bible condoning, or even promoting, rape. However, the passage says nothing about raping the captive women. It is wrong to assume that the captive women were to be raped. Again, Deuteronomy 22:25-27 condemns rape, even advocating the death penalty for perpetrators of rape. In the Numbers 31 passage the soldiers were commanded to purify themselves and their captives (verse 19). Rape would have violated this command (see Leviticus 15:16-18). The women who were taken captive are never referred to as sexual objects. Did the captive women likely eventually marry amongst the Israelites? Yes. Is there any indication that rape or sex slavery was forced upon the women? Absolutely not.
In the New Testament, rape is not mentioned directly, but within the Jewish culture of its writers, rape would have been considered as sexual immorality. As such, both Jesus and His followers (including the apostle Paul) spoke against sexual immorality, even offering it as justifiable grounds for divorce when a person actively committed sexual acts outside of the bond of marriage (Matthew 5:32). This would not, however, apply to the victim of rape, only the one who committed the act.
Further, the New Testament is clear that Christians are to obey the laws of their governing authorities (Romans 13). Not only is rape morally wrong; it is also wrong according to the laws of our governing authorities. As such, anyone who would commit this crime should expect dire consequences, including arrest and imprisonment.
No. 7 Thou shalt no commit adultery
Rape is a form of adultery (unless you're married).
Jesus tells us how to interpret the commandment not to kill, namely that it is even a sin to call your brother stupid. I think it is fair to say that Jesus generalized that commandment to one that absolutely forbids violence against persons, be it physical or "only" verbal.
Of course, this would also cover rape.
I've heard that the 10 commandment is there for "category" of prohibition. Rape would go to don't steal I guess. By raping you are stealing "usage right" from the girl or the parent.
In a sense rape is indeed prohibited. In ancient hebrew, rape is actually punished by fine that can be quite high. That's how we define something as prohibited, namely that there is a punishment.
The difference is on what's the punishment and how do we measure damage.
In ancient time they don't have jail. Jail is a very expensive innovation. So the only punishment besides stoning possible are either fine or canning.
Jewish halakha actually prescribe that the rapists must pay for the pain and for the drop of the market value of the girl. The 50 shekel is only for the pleasure
The judge would estimate how much the girls' market value is. Maybe the judges would auction of the girl and shill bid it to get the correct market value of the girl as sex slave. Maybe they just estimate. Got to ask the jews again.
So raping Selena Gomez is still off the chart. In ancient time people do not have bankruptcy laws. So if you can't pay you become slaves, which is like going to jail.
Some may think it's disgusting. However, we may have to consider:
I will have to ask the jews again now that we can decide fatherhood by DNA tests, what would Rabam says about sex outside marriage and rape.
Jews do not think sex outside marriage as a big deal. It never get death penalty. Only on some circumstances it can get pretty serious.
Which explains why prostitution is legal in Israel I guess.
Because the 10 Commandments have little to do with ethics and everything to do with (a) creating an orderly society and (b) distinguising the Jewish community from its neightbours. Women were generally regarded as property by the culture of the time, which wrote the commandments.