What does Romans 12:9 mean?

In Romans 12, Paul is describing what it means to live the Christian life. How should we respond to God's great mercy toward us? Paul's first response is that we should figure out what spiritual gift or gifts God has given to us, then actually use those gifts to serve other Christians in the church.

Now he begins a list-like section of quick commands about how Christians should lead their everyday lives. We all know that we should love each other, but Paul's instruction is that our love must be genuine or sincere. In other words, Christians are not called to fake an attitude of love for each other, but to find ways to express God's love meaningfully, as an extension of God's love for us and ours for Him.

Next, Paul uses a strong word often translated as "hate" or "abhor." This is the Greek term apostygountes, which implies a dislike or revulsion towards something. Proverbs 6:16–19 describes seven things God hates, using the equivalent Hebrew term. None of these hated things are people; all of them are sin. Christians, too, are called to learn to hate what is evil, meaning sin. This is especially true of sin that brings harm to the innocent. This is one of the ways we need to be transformed to think like God (Romans 12:2). Hating evil, especially the sins that intrigue us, does not always come naturally.

Finally, Paul commands us to hold fast to, or cling to, what is good. Again, it can sometimes be hard to know what is truly good. We must learn to see the world through God's perspective, to deeply invest our time and energy in securing and keeping what is truly "good."