'Swear' in the Bible

And they say, 'We give back, and of them we seek nothing; so we do as thou art saying.' And I call the priests, and cause them to swear to do according to this thing;

“You provided bread from heaven for them for their hunger,You brought forth water from a rock for them for their thirst,And You told them to enter in order to possessThe land which You swore to give them.

And I contended with them, and cursed them, and smote certain of them, and plucked off their hair, and made them swear by God, saying, Ye shall not give your daughters unto their sons, nor take their daughters unto your sons, or for yourselves.