After reading the Parsha of Maaseros in Reeh, the king would skip to read the Parsha of Vidui Maaser in Parshas Ki Savo, so that the 2 Parshios of Maaseros could be read consecutively, without any interruption.
The Parshios of Maaseros were read because Hakhel took place at the end of the Shemittah year, where no Maaser was separated. They would read it at Hakhel as a reminder that now, the laws of Maaser would apply once more.
The king would then go back to read the Parsha of the King in Shoftim and would then jump back to Ki Savo to read “the blessings and the curses”.
This refers to the blessings and curses that would be proclaimed on Har Gerizim and Har Eival upon entering the Land of Israel and also to the passage of the Tochecha, which describes the blessings for fulfilling the Mitzvos and the punishments for failing to observe them.
These blessings and curses were included in the reading, because the objective of Hakhel is to cause the Jewish people to have Fear of Heaven and to inspire them to guard, to observe all of the words of this Torah”, referring to the Mitzvos.
