A Sense of Responsibility
This is what our ancestors heard when they entered Eretz Yisrael and stood on Mount Gerizim and Mount Eyval. It was the conclusion of a series of eleven pronouncements uttered by the Levites, first in the form of a blessing and afterwards as a curse for those who did the opposite.
While the simple meaning of this is that a Jew must believe that every one of the Torah's commandments is from G-d even if he fails to always observe them, there is another meaning as well. In his commentary on Chumash, Ramban cites the Jerusalem Talmud's interpretation of this blessing and curse as relating to one who has the power to influence others to be loyal to the Torah.
This sense of responsibility to a fellow Jew was dramatically communicated to our people as soon as they entered their Promised Land and is one that must be preserved to secure this Land for us forever.