'Oath' in the Bible

May God's punishment be on Abner, if I do not for David as the Lord in his oath has said,

Then they came to urge David to eat bread while it was still day, but David took an oath: “May God punish me and do so severely if I taste bread or anything else before sunset!”

Now at the end of four years, Absalom said to the king, Let me go to Hebron and give effect to the oath which I made to the Lord:

For while I was living in Geshur in Aram, your servant made an oath, saying, If ever the Lord lets me come back to Jerusalem, I will give him worship in Hebron.

So get up now, and go out and say some kind words to your servants; for, by the Lord, I give you my oath, that if you do not go out, not one of them will keep with you tonight; and that will be worse for you than all the evil which has overtaken you from your earliest years.

So the king said to Shimei, “You will not die.” Then the king gave him his oath.

The Gibeonites were not Israelites but rather a remnant of the Amorites. The Israelites had taken an oath concerning them, but Saul had tried to kill them in his zeal for the Israelites and Judah. So David summoned the Gibeonites and spoke to them.

But the king spared Mephibosheth, the son of Jonathan the son of Saul, because of the LORD'S oath that was between them, between David and Jonathan the son of Saul.

But Abishai the son of Zeruiah came to David's aid, striking the Philistine down and killing him. Then David's men took an oath saying, "You will not go out to battle with us again! You must not extinguish the lamp of Israel!"