More than 35 articles in the Islamic Penal Code are related to the subject of oath. One of the controversial issues regarding oaths is those who have to swear; In the first place, the oath is specific to the relatives of the victim and in some cases, it is rejected by the person suspected of murder. The question is, who are the swearers and what is their relationship with the victim (or killer)? Despite its importance, this issue has been less raised in the words of the jurists, while in practice, the execution of the oath depends on it. There are five possibilities and four promises in this regard: the actual heirs, the classes of inheritance (including the actual and potential heirs), the absolute relatives, the tribe and the absolute, the rijals. It is a famous saying among the jurists of the tribe and tribe of the slain. In this article, we have strengthened the promise of relatives, which is also approved by the Penal Code. Our evidence for this statement: The Qur'an is the appearance of narrations, the words of jurists, and the wisdom and philosophy of oath legislation.