“It is true that some preach Christ out of envy and rivalry, but others out of goodwill. The latter do so out of love, knowing that I am put here for the defense of the gospel. The former preach Christ out of selfish ambition, not sincerely, supposing that they can stir up trouble for me while I am in chains. But what does it matter? The important thing is that in every way, whether from false motives or true, Christ is preached. And because of this I rejoice. Yes, and I will continue to rejoice,” – Philippians 1:15-18 NIV

Paul says that what is significant in preaching the Gospel with false motives such as doing it out of envy or pride or whatever non-sincere way, is that the Gospel is being preached. It matters less the reasons why and more about the fact that it is. I’d also like to add the context of 1 Corinthians 12:3 to this passage, which says this:

“Therefore I want you to know that no one who is speaking by the Spirit of God says, “Jesus be cursed,” and no one can say, “Jesus is Lord,” except by the Holy Spirit.” – 1 Corinthians 12:3 NIV

It is only by the Holy Spirit in which we can say that Jesus is Lord, so this might be some valuable context to the original passage. If all of the discussion about Christ, in reality, is the work of the Holy Spirit, well then it most definitely would be a good thing to see anyone and everyone preaching the Gospel. What can we take away from this then? Let us never discourage anyone from sharing the Gospel whether they are a Christian or not or qualified or not or your enemy or not or whatever as long as they aren’t teaching a false Christ. What we should do is equip them and help them to preach the Gospel even better to win more souls for the kingdom.