Augustine of Hippo

There were in the times of the apostles some who were preaching truth but not in truth, that is, not in a true spirit. Of these the apostle says that their proclamation was not pure but was preached "through envy and rivalry." Even though they were tolerated who proclaimed the truth without purity of mind, they were not praised, as if to assume that they were preaching with a pure mind. So Paul says of them that, whether in pretense or in truth, Christ is proclaimed. Yet he certainly does not imply that Christ may now be denied in order to be later proclaimed.