“The day of Yahweh

Is near

Against all the nations.

As you have done,

It shall be done

To you.

Your deeds

Shall return

On your own head.”

Obadiah warned that the day of Yahweh, as in the prophet Amos, was coming to all the countries, since it was near.  As they have done, so it shall be done to them, since their deeds would return to their own head.