Parker said Thomas told him a judge should be evaluated by whether he faithfully upholds his oath to God, not to the people, to the state or to the Constitution.
If this is true, and I suspect that it is, what Thomas said is ultimately true. Ultimately all persons will stand before the judgment seat of Christ. Mortal Alabama justices, however, are not authorized to sit in that chair. Neither are U.S. Supreme Court justices. All earthly justices are authorized to do is to fulfill their oath to uphold the laws of the people as embodied in the statues of their state and the Constitution.
An interesting discussion of the propriety of Thomas' remarks is already under way at Sam Heldman's blog.