Adam Clarke on Obadiah 1:17

But upon Mount Zion shall be deliverance - Here is a promise of the return from the Babylonish captivity. They shall come to Zion, and there they shall find safety; and it is remarkable that after their return they were greatly befriended by the Persian kings, and by Alexander the Great and his successors; so that, whilst they ravaged the neighboring nations, the Jews were unmolested. See Calmet.

And there shall be holiness - They shall return to God, separate themselves from their idols, and become a better people than they were when God permitted them to be carried into captivity.

The house of Jacob shall possess - They were restored to their former possessions. But this may refer also to their future restoration under the Gospel, when they shall be truly converted, and become holiness to the Lord; for salvation and holiness shall be the characteristics of Zion - the Christian Church, for ever.