Two words about loyalty
Right after "Do not murder" comes the seventh commandment, also two words in Hebrew.
Rashi (Rabbi Shlomo Yitzchaki, France, 1000s, the classic commentator on the Torah) explains what the word means:
In other words, this commandment protects marriage. In the Torah's own language, ni'uf means a married woman being unfaithful to her husband, together with the man involved. The prophet Malachi, below, speaks just as sharply to husbands who betray their wives.
The Torah has other laws about relationships (the main chapter is Vayikra 18). They are learned in their own place, with a teacher, and this page does not go into them. It is about the idea at the center of the seventh commandment: loyalty.
A covenant, with Hashem as witness
The prophet Malachi calls marriage a brit, a covenant.
Malachi is speaking to men of his time who had broken faith with their wives. He calls the marriage a brit, the same word the Torah uses for Hashem's covenant with the Jewish people, and he says Hashem Himself is the witness. Being unfaithful is not only a wrong against a husband or a wife. It breaks a promise that Hashem witnessed.
The prophets also say it in the other direction, describing Hashem's bond with the Jewish people as a marriage. Hoshea says in Hashem's name:
If you put on tefillin, you may know these verses: many siddurim have you say them every weekday morning while you wind the strap around your finger. The relationship with Hashem is a kind of marriage, and a marriage is about faithfulness. That is how the Mechilta explains where this commandment sits on the tablets.
Opposite “You shall have no other gods”
Read straight across the two tablets, and the seventh commandment lines up with the second.
In one view in the Mechilta (an early midrash on Shemot from the Sages of the Mishnah), the Ten Commandments were written five on each tablet. Then every commandment on one tablet faces a partner on the other: the first with the sixth, the second with the seventh, and so on.
In plain words: serving something other than Hashem is being unfaithful to Him, the way someone who breaks a marriage is unfaithful to his spouse. The two commandments describe the same failure of loyalty, once toward Hashem and once toward a person. The verse the Mechilta brings from Yechezkel is the same one Rashi brings to explain the word ni'uf.
The Mechilta adds a verse from Hoshea that makes the same point. This pairing is the view of Rabbi Chananya ben Gamliel (in some editions, Chanina). The Sages there disagree and say all ten were written on each tablet (Mechilta, Bachodesh 8).
Yosef says no
Yosef was a young man far from home, a slave in Egypt, trusted with everything. Then came the test. Step through it.
Look at the reasons Yosef gave. He did not say no one would find out, or that he was strong enough to handle it. He said his master had trusted him with everything, and that it would be a sin against God. And when she grabbed him, he left.
The eyes and the heart
Twice a day, in the Shema, we say it: do not stray after your heart and your eyes.
This verse is in the third paragraph of the Shema, the paragraph about tzitzit. Rashi points out that the word for "wander," taturu, is the word the Torah uses for the spies who scouted the Land of Israel. The eyes and the heart are scouts too:
Three steps, and three places to stop. Choose a step.
Iyov did not wait for the test to make up his mind. He made his covenant ahead of time.
When you want it, and say no
The Mishnah does not pretend this is easy.
Notice what the Mishnah takes for granted: a person's soul desires these things. The reward is for keeping away anyway, and it reaches his children's children.
Just before this, in the same Mishnah, Rabbi Shimon learns the idea from the Torah's chapter on forbidden relationships itself:
In the Gemara, Rav Tuvi bar Rav Kisna points out a contradiction to Rava: one teaching rewards only someone who does a mitzvah, and another rewards someone who just sat and did not sin. Rava answers:
Yosef in Potiphar's house is a case like that.
Where this page stops
This page teaches an idea. Some things belong in a conversation with a person, not on a web page.
One of the three
Rabbi Yochanan, in the name of Rabbi Shimon ben Yehotzadak, reports that the Sages voted on this in Lod. Two of the three, idol worship and forbidden relationships (which include adultery), are this page's pair on the tablets.
The details are learned with a teacher
The laws of relationships, in Vayikra 18 and in the Shulchan Aruch (the standard code of Jewish law), are learned with a rebbe or a rav, at the right time and in the right setting. This page does not teach them.
Questions go to a person
If you have a question about this commandment, or something you are struggling with, talk to a rebbe, a rav or a parent you trust. Asking for guidance is part of guarding yourself, not a sign that you failed.
If something feels wrong. This page is for learning. If anyone has made you uncomfortable in a way that feels wrong, telling a trusted adult is the right thing to do: a parent, a teacher, a school counselor or a rav.
Common questions
Short answers, with sources.
What does lo tinaf mean?
It is the seventh of the Ten Commandments (Shemot 20:13; Devarim 5:17). Rashi explains that the word ni'uf is used only about a married woman: the commandment protects marriage (Rashi on Shemot 20:13). One view in the Mechilta sets it opposite the second commandment and compares serving idols to being unfaithful in a marriage (Mechilta, Bachodesh 8).
Why compare idol worship to being unfaithful in a marriage?
Because the Jewish people's relationship with Hashem is a covenant, and the prophets describe it as a marriage (Hoshea 2:21-22). Serving another god breaks that covenant, the way being unfaithful breaks a marriage (Mechilta, Bachodesh 8, quoting Yechezkel 16:32).
Why is Yosef the example?
Because the Torah tells his story in detail. He was young, alone and a slave, he was pressured day after day, and he said no, out of loyalty to the man who trusted him and to Hashem (Bereishit 39:8-10). The Gemara calls him Yosef HaTzaddik, Yosef the righteous (Yoma 35b).
What does "guarding the eyes" mean in practice?
The Torah's words are in the Shema: do not stray after your heart and your eyes (Bamidbar 15:39), and Iyov describes a covenant he made with his eyes (Iyov 31:1). How this applies to what you see every day, including screens, is a question to work out with a rebbe or rav you trust.
Is it a sin to have a thought?
Thoughts come to everyone. The Torah asks you not to "wander after" them (Bamidbar 15:39), and the Mishnah promises a reward for holding back from what you want (Makkot 3:15). Where the line is between a thought that passes and one you are chasing is a good question for a rav.
Where can I learn more?
With a rebbe or a rav. The halachot of relationships are taught in their own setting. On this site, the pages below cover the rest of the Ten Commandments.
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