Parshas Mattos begins with a survey of the laws of oaths addressed to the tribal leaders.  Why specifically the tribal leaders? While Mattos may begin with the laws of oaths and vows, it concludes with the leaders of two tribes requesting that they settle the other side of the Jordan and committing to go and fight with the other tribes until they succeed in their wars.  Both times a similar phrasing "kol hayotze mepif taaseh" "that which comes from your mouth you shall do" is used.  But while Avraham bound Eliezer and Yaakov bound Yosef with oaths, Moshe asks no oath of them. He simply tells them that they must keep their word and that there will be consequences if they do not. Indeed there are two tragic oaths that will later follow, by Yiftah, who vows to sacrifice whatever comes to meet him on his return home, and Shaul, who vows that he will kill anyone who breaks his pledge to eat nothing until the enemy is defeated only to have his son Yonatan unknowingly eat ...