I want to start with the haftorah rather than the parasha, since this is Shabbat Nachamu and we get the name from the haftorah.
What does נחמו mean? The King James Bible translates it as “Comfort ye, Comfort ye”; not “you will be comforted” but a command to the navi and others (it’s plural; who else is being commanded?) to comfort בני ישראל. And what is that comfort? פנו דרך ה׳; ישרו בערבה מסלה לאלקינו. Make a highway for ה׳. Not “ה׳ has forgiven you” or “ה׳ will rebuild the מקדש”, just a voice calling out that you need to start paving the road. What kind of comfort is that?
Hold that thought. I want to look at the halacha in the שולחן ערוך:
And the Chofetz Chaim brings a straightforward explanation for the halacha:
And that is the usual explanation, bringing us from the איכה of Moshe to the איכה of Yeshaya to the איכה of Yermiyahu. But that’s not what the words say! The halacha is not that דברים comes before Tisha B’Av (like במדבר comes before Shavuot) but that ואתחנן comes after Tisha B’Av.
I think that the שולחן ערוך is saying that the critical thing to learn from the parasha is not the תוכחה before Tisha B’Av; we get plenty of that. It is the נחמה afterward. The plural נחמו refers to all of us; we need to call out the נחמה. And just like the haftorah is one of נחמה, the parasha itself contains נחמה:
The נחמה here is that you have lots of hard work ahead, תדרשנו בכל לבבך ובכל נפשך. It will not be easy and the final redemption will not be handed to you, but be reassured that it will come: באחרית הימים ושבת עד ה׳ אלקיך ושמעת בקלו. Similarly the metaphor of Yeshaya: You need to build the road. ה׳ will help, lowering the hills and raising the valleys, but the work has to come from you. And eventually, your work will bear fruit: ראו כל בשר יחדו כי פי ה׳ דבר.
And the structure of ואתחנן demonstrates this principle. ספר דברים is basically a long speech by Moshe, starting with a historical introduction then going through all the laws that בני ישראל will need. But there is an interruption:
Instead of going from ד:מ to ה:א, Moshe stops for a demonstration, a kind of multimedia presentation of how to do mitzvot. But the mitzvah he chooses isn’t really a mitzvah, as Rashi points out:
Moshe is showing that even after the depredations of בעל-פעור and his own failure to enter Israel, the response has to be to take whatever steps are possible to begin the process of return. Yes, the work is hard. Yes, we may not see the fruits of our own labor. But the fact that it is possible to start working again is itself the greatest נחמה.