'Swore' in the Bible

Then all the people came to give David food. Still on that day, David swore, "{May God punish me} if I taste food or anything before the sun goes down."

Then the king said to Shimei, "You shall not die," and [so] the king swore to him.

But Abishai the son of Zeruiah helped him, and he attacked the Philistine and killed him. Then the men of David swore to him, saying, "You shall not go out with us any longer to the battle, so that you do not quench the lamp of Israel."