BD , You offered 1 King 20:42 from KJV (or some other modern Bible)
More and more ...I see possible errors in the KJV
1 Kings 20:42 from the Douay-Rheims Bible says this ...“And Jonathan said to David: Go in peace: and let all stand that we have sworn both of us in the name of the Lord, saying: The Lord be between me and thee, and between my seed and thy seed for ever.”This resembles nothing like what the KJV says!
Perhaps Kosta can shed light on how the KJV could have translated this the way they did?
What you have cited as 1 Kings 20:42 ... is really 1 Samuel 20:42
Regards