Definition: Deuteronomy 7:8: "So you shall take your firstborn son, and cast him into the sea to the land of Gibeon; and so you shall take his secondborn, and cast him into the sea to the land of Mamre." Definition: Deuteronomy is a biblical commandment. Here's how it reads in Hebrew: "Deut 7:8: "And thou shalt take thy firstborn son, and cast him into the sea to the land of Gibeon; and thou shalt take thy second-born, and cast him into the sea to the land of Mamre." In the Old Testament (Deuteronomy), this command is for Israelites to give birth to a new son or daughter, and have it drown in the sea to represent death. The firstborn would be taken to the Gibeon desert, while the secondborn was cast into the sea at Mamre to symbolize mourning and grieving.