Ammon knows that slavery is not an option in his land, and so notes. What is interesting in these two verses is the conjunction “but” at the beginning of verse 10. Why this “but?”
Ammon suggests that even though the voluntary slavery is not an option, that they should nevertheless go and rely on the mercies of the Zarahemalites. It is to this last suggestion that the King adds his “but.” Rather than go to rely on the mercies of men, the King reminds Ammon to go to the Lord. The King will rely upon the mercies of the Lord, not the mercies of men.