KJV Isaiah 13:15 Every one that is found shall be thrust through; and every one that is joined unto them shall fall by the sword.

The Hebrew word translated as 'joined' is ספה, but does not mean 'join,' but instead 'to be swept away' or 'captured.' Most of the modern versions translated this passage correctly, such as seen in the RSV, '...and whoever is caught will fall by the sword.'

It is most likely that the KJV translator misread the Hebrew word ספה for the word ספח, which does mean 'to join.' Notice that these two words are identical, with the exception of slight difference in the last letter. On the right is the letter hey, while on the left is the letter hhet, it is an easy mistake, but a mistake non-the-less.