The latter do it out of love, knowing that I am put here for the defense of the gospel. (ESV)
Paul is imprisoned. And some of his peers were preaching the Gospel alongside him as co-laborers in the Lord. Others were preaching, but were trying to rival Paul, envious of his ministry and actually rooting against him. In verse 16 Paul refers to those who were preaching out of love. These were true ministers in the faith, with hearts of good will.
It would be delightful if all preachers of the Gospel could work together for a common goal of seeing lives rescued from the pit of hell. Sadly, there are those who compete against one another. We live in a time of great division. Political viewpoints are no longer discussed in a gentlemanly fashion. Opposing viewpoints are demonized. We fight against one another, not for one another.
Those who preach the Gospel need to remember what the Gospel is. The Gospel is a message of God's great love to mankind that transforms them from being spiritually dead and under God's wrath to becoming the very children of God, and heirs of eternal life. This is a message that we ought to be united about.
Someone may share that message a little differently. Some may have what seems like greater success than us. That should not change our love and support for those who carry the same message. Paul was blessed by those who were aware that he had laid it all on the line for Christ. As a result, he was in prison. He was encouraged by those who also loved enough to preach the Gospel for the right reasons. They were his true brothers in Christ.
Can you be united with your brother and sister in Christ? There is no place for rivalry and envy. We are on the same team. Let's love one another and passionately share the Gospel!