Adam Clarke on Isaiah 16:4

Let mine outcasts dwell with thee, Moab "Let the outcasts of Moab sojourn with thee, O Zion" - Setting the points aside, this is by much the most obvious construction of the Hebrew, as well as most agreeable to the context, and the design of the prophet. And it is confirmed by the Septuagint οἱ φυγαδες Μωαβ, and Syriac.

The oppressors "The oppressor" - Perhaps the Israelites, who in the time of Ahab invaded Judah, defeated his army, slaying one hundred and twenty thousand men, and brought the kingdom to the brink of destruction. Judah, being now in a more prosperous condition, is represented as able to receive and to protect the fugitive Moabites. And with those former times of distress the security and flourishing state of the kingdom under the government of Hezekiah is contrasted.