Parshat Ki Tavo (Rabbi Sedley)

Our Torah reading gives the commandment for the Jewish nation to recite the blessings and curses on Mount Gerizim and Mount Eival, after they have entered the Land of Israel. The Mishna (Sota 7; 5) describes how this took place: "Once the Jews had crossed the Jordan river and come to Mount Gerizim and Mount Eival which are in the Shomron; Six of the tribes ascended Mount Gerizim, and six ascended Mount Eival, while the Cohanim, Levi'im and the ark remained in between at the bottom. They turned towards Mount Gerizim, and began with the blessing, 'Blessed is the person who shall not make a graven or molten image' and all the people answered 'Amen'. Then they turned toward Mount Eival, and recited the curse 'Cursed is the man who will make a graven or molten image' (Deuteronomy 27; 15), and all the people answered 'Amen'. This continued until they had completed the blessings and the curses."
The problem with this Mishna is the fact that the Torah doesn't actually list the blessings that are mentioned. In our Torah reading we only have the curses. We have to rely on the principle (Nedarim 11a) that from a negative we can infer the positive to work out that we should recite the blessings also.
The Torah always tries to use positive language. Why in this case did G-d only give us the curses? Would it not have been better to list the blessings and leave us to deduce the curses on our own?
We know that there is nothing which remains stationary, either physically or spiritually. Anything which is not moving upwards is decaying downward. This is explicit in several places in the Mishna, e.g. "Hillel said ...He who does not increase his knowledge decreases it" (Chapters of the Fathers 1; 13). Using this concept we can explain why the Torah only listed the curses. Had we been given only the blessings, we might have thought that keeping the Torah led to blessing, but not keeping the Torah had no consequences. However, since the Torah lists the destructive results of transgression, we can infer the blessings that come into the world through observance. The Torah is teaching us that there is no such thing as taking 'time out', and doing actions which have no consequence whatsoever. Every act that we do either brings blessing into the world, or the opposite, there is no such thing as a 'pareve' action.
The Kli Yakar gives another two explanations. Firstly he explains (verse 12) that the main blessing which is promised will only occur in the World-to-Come, which is hidden from us now. As a sign that the real reward is not in this world, G-d chose to hide the formulation of the blessings, so that they are not explicit in the Torah. The reason that the reward must be in the World-to-Come is in keeping with the Talmudic maxim that the reward from G-d is always far greater than the punishment. Though G-d will "visit the sins of the fathers on the sons and grandsons for four generations" (Exodus 33; 7), the reward is for one thousand generations (Deuteronomy 7; 9). The consequences of Mitzvot are thus 250 times more powerful than the results of sin. Thus, though a sin could be punished in this world, reward for Mitzvot occurs only in a world which is infinite. Since it has no physical constraints there is no limit to the effects of the Mitzvah.
Alternatively the Torah tells us the curses, because we know that through the repentance process sins and curses can be turned into merits and blessings. "Reish Lakish said, 'how great is repentance, for through repentance premeditated sins are accounted as merits, as it is said (Ezekiel 33; 19) "When a wicked man returns form his wickedness and practices justice and charity, he shall live because of them"" (Yoma 86a). Therefore the Torah gives us the curses, not only to infer the blessings from them, but to teach us that through repentance the blessings can actually be contained within the curses.

Ki Tavo summary

When the Israelites enter the Land of Israel, they should bring the first fruits from their trees each year to Jerusalem and offer them at the Temple. As they place the fruits before the altar they recite a paragraph which mentions the origins of the nation as slaves in Egypt, and that G-d in His goodness brought them out of slavery and into the Land of Israel. One tithe (ten percent) of the crops from the third and sixth year shall be given to the poor. This replaces the normal tithe which is to be eaten by the farmers in the city of Jerusalem. These tithes may not be eaten when in a state of mourning, nor used to pay for funeral expenses.
Because the Jews accepted these commandments upon themselves, and dedicated themselves to serving G-d, He has also chosen them as His treasured nation. Moshe and the elders command the nation that when they enter into Israel they must renew their covenant of Torah. They shall take rocks from the Jordan river, set them up as monuments and inscribe the whole of the Torah on them. After this, six of the tribes shall stand on Mount Gerizim and six on Mount Eival. The Cohanim and Levi'im shall stand in between these two mountains and read out the blessings and curses for the nation. After each blessing or curse all the people shall answer 'Amen'. The curses are listed, as are the blessings. If the Jews observe all the laws in the Torah they shall receive material and spiritual blessing and success. They will be invincible in the face of their enemies, and shall be a major world superpower. If they fail to keep the commandments then they will be beset by the curses. They will not prosper materially, and will be conquered by their enemies. They will perish from famine and thirst, and will not know where to turn. Their children will be taken away and they will go mad from the pain and suffering that will surround them. All the nations of the world will talk about how far they have fallen and the calamities that have befallen them. They will be sent into exile, and their numbers decimated. And even in exile there will be no rest, but still they will suffer and be persecuted. These are the words of the covenant which G-d commanded Moshe to seal with the Children of Israel before entering the Land of Israel.
Moshe gives final encouragement to the people, and reminds them of all that they have been through and all that G-d has done for them. He urges them to keep the covenant.