Only the Jewish people can do the Avoda of Beirurim-Mashal of precious stone of king:
The Avoda of Bnei Yisrael is to refine the sparks of Tohu that fell into Tikkun. This job cannot be done by Gentiles. This is similar to a precious gem that fell off the king’s crown and cannot be found. The King summons his son to find the jewel in order to merit him in the great deed. He does not allow the other servants to look for it, as his entire desire is to merit his son.
 Or Torah [Maggid] Vayeishev 51