John MacArthur, commenting on the controversies he has addressed over the years:
Reflecting on all those controversies, what is most surprising is that in every case, the threat I was writing about had originated within the evangelical movement. When I was in seminary, I had prepared my mind and heart to answer assaults from the world against the authority of Scripture and the truth of the gospel. I did not anticipate that so much of my time and energy would be spent trying to defend the gospel against attacks from inside the visible church—including assaults on gospel truth from respected leaders in the evangelical movement.
—John MacArthur, The Gospel according to Paul (Thomas Nelson, 2017), xxv.
My observation is the same. It seems to me that a lot of energy is expended worrying about, and warning against, threats from the world, while heresies in the form of “worship” songs and the latest pop-theology books slip in unnoticed and unexamined. The sheeps’ clothing grows thinner, yet the wolves remain unrecognized.
Source: Threats from Within