This week's section begins with the laws of vows. If a Jew makes a vow to do or to abstain from doing something it becomes a sin to break that vow and an obligation to fulfill it.
This shows the power of speech. Just by uttering a few words, for instance, "I swear to eat that pickle" a plain pickle becomes as a 'mitzvah'.
This week we read the second to last Torah portion in the book of Numbers.
It begins with the laws of negating vows, continues with the spoils taken after defeating the nation of Midian and concludes with what happened when the tribes of Gad and Reuven decided not to settle in Israel.