'Sware' in the Bible

And all the people came to cause David to eat bread while it was yet day; but David sware, saying, God do so to me, and more also, if I taste bread, or aught else, till the sun be down.

And the king said unto Shimei, Thou shalt not die. And the king sware unto him.

But Abishai the son of Zeruiah succored him, and smote the Philistine, and killed him. Then the men of David sware unto him, saying, Thou shalt go no more out with us to battle, that thou quench not the lamp of Israel.