'Oath' in the Bible

Why then hast thou not kept the oath of Jehovah, and the commandment that I have charged thee with?

If a man sin against his neighbor, and an oath be laid upon him to cause him to swear, and he come and'swear before thine altar in this house;

As Jehovah thy God liveth, there is no nation or kingdom, whither my lord hath not sent to seek thee: and when they said, He is not here, he took an oath of the kingdom and nation, that they found thee not.