The first aliyah discusses laws of verbal vows by means of which someone obligates himself or herself with a vow. Such a person must do all that he vows. Then the aliyah gives the laws of a woman who makes a vow and how her husband or father, under certain circumstances, can overturn such vows.
The Torah continues with G-d commanding Moshe to take revenge against the Midianites, after which time Moshe shall pass away. This aliyah describes the war taking place with an army of 12,000 Jews. All adult males of Midian as well as their five Kings are killed in this battle. The non-Jewish prophet Bilam, who was the main subject of parsha Balak that we read two weeks ago, dies in this war.