John Gill Commentary Luke 23:37

"and saying, If thou art the King of the Jews, save thyself." — Luke 23:37 (ASV)

And saying, if you are the King of the Jews
Or their Messiah, who was spoken of as a divine person; for otherwise he might have been their king, and not have been able to have done what is proposed:

save yourself :
or deliver yourself from the cross.