'Oaths' in the Bible

Again, ye have heard that it was said to them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths:

And the king was grieved; but for the sake of his oaths, and of them that sat at meat with him, he commanded it to be given;

And the king was exceeding sorry; but for the sake of his oaths, and of them that sat at meat, he would not reject her.