"During the reign of Benedict XVI in 09, Piper was asked on video if he had two minutes to question the Pope on an issue, what would he ask, and he chose the subject of justification.
"I think Rome and Protestantism are not yet ready ‚Äď I don't think the Reformation is over..." he said in the video.
"He then proceeded to detail the question he would ask the Pope. "'Do you teach that we should rely entirely on the righteousness of Christ imputed to us by faith alone as the ground of God being 100% for us, after which necessary sanctification comes? Do you teach that?'" he said in the clip.
"And if he said, 'No, we don't,' then I'd say, 'I think that right at the core of Roman Catholic theology is a heresy,' or something like that," he added.
"In a new post on Thursday, however, Piper conceded that 'heresy' is a strong word and attempted a more nuanced explanation of what he meant by his comments.
"I am thankful that God is willing to save us even when our grasp of the gospel may be partial or defective."
For Piper, as of today, the Reformation is officially over.