What is the favorite Scripture they use to promote this?
It is Romans 4:25. They believe right here in this verse, St. Paul is teaching a justification that occurred without any reference to faith
Here is an example.
1.) From again Steadfast Waltherian group found here, Jim Pierce writing:
In wrapping up my answer, we can talk about the entire human race, or the world, being justified—just as the Scriptures do (Ro 4:25)—as the action God took in response to Jesus’ resurrection from the dead where the Law is concerned2.) From my interaction with one adherent of UOJ:
ME: "Joe it is different because Brett and I do not believe in the starting point that there is justification that has happened FOR all men without faith or without regard to faith. That is difference. The difference is that we do not posit or assert a universal justification."
Joe: You are speaking against Romans 4:25.
3.) Again from a post just recently by a Steadfast Waltherian blogger found here. To prove the existence of an objective justification that occurred outside of faith, the blogging pastor says this (apparently taken from Francis Pieper):
Romans 4:25: He was delivered over to death for our sins and was raised to life for our justification. “To refer to the words: Who was raised again for our justification,” to the so-called subjective justification, which takes place by faith, not only weakens the force of the words, but also violates the context.”3
It is evident just from the sampling on how Romans 4:25 is being used that without a doubt, UOJers in general and the Steadfast Waltherians in particular believe in a justification that occurred without reference to faith.
What does Aegidius Hunnius say?
Hence Paul, when he expressly discusses justification in Romans 3 and 4, does not know of a justification apart from faith, and especially as Galatians 2 plainly says, "Man is not justified except by faith in Jesus Christ."
Did you read that? According to Hunnius, in Romans 3 and 4, St. Paul DOES NOT KNOW OF A JUSTIFICATION APART FROM FAITH.
Since UOJers are quoting Romans 4:25 to prove this, and obviously verse 25 is part of Romans 4, these people I quoted above KNOW of a justification without faith. Here Hunnius, a well known old orthodox Lutheran assails them or they boldly contradict him.
This is where American Synodic Lutherans are peculiar to the rest of the Protestant world. It is only they who take Romans 4:25 that way. They are also peculiar amongst the rest of the Lutheran world! According to Bruce Church if we count the Lutherans who believe this stuff, there are only 2.5 Million of them who teach this stuff, out of some 45 Million (or so) Lutherans in the world.
The Hunnius quote I provided proves that the Steadfast Waltherians are Huberites or at least shares the conviction of Huber on this point...and that is not a good thing. If I were you I won't get involve with that. False teaching is a dangerous thing and we ought to be fearful of it. I know I am.