Philippians 1:16 - Coke's Commentary on the Holy Bible

Not sincerely,— This may refer to the matter of their preaching: it was not sincere, pure, and uncorrupted gospel; but they adulterated it, by mixing Judaism with it; and so they perverted the gospel of Christ. Galatians 1:7. Or it may refer to the intentions of the preachers: they acted not sincerely in what they did; but while they pretended their great end was to preach Christ, instead of that they made it their chief business to preach down the Apostle, and to lessen his reputation. The next words seem to support the latter sense, as does what he says in Philippians 1:18. See the Introduction to this chapter.