Ezra 4:1

Now when the adversaries of Judah, &c. The Samaritans, the relics of the ten tribes, and foreigners that had joined themselves to them, and patched up that mongrel religion of which we had an account 2 Kings 17:33, where it is said, They feared the Lord, and served their own gods. They are called the people of the land, Ezra 4:4. Thus, the worst enemies that Judah and Benjamin had were those that said they were Jews, and were not.