The image of those who advance the gospel is not all positive. The motives of some are not pure: they proclaim Christ out of envy and rivalry. It is not clear exactly which people Paul is thinking of. They are certainly not false teachers, against whom he warns strongly in other letters, for example in Galatians 1:1–24 (another gospel) and Philippians 4:2. He says here three times (Philippians 1:15, Philippians 1:17, Philippians 1:18) that Christ is proclaimed. It must have something to do with their attitude toward Paul (see Philippians 1:17). Fortunately, there are others who proclaim Christ with good intentions. Their relationship with Paul is good, their motives are pure.
15 Some indeed preach Christ from envy and rivalry, but others from good will.