Answer: Christ was living in Paul, (verse 20).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
John 14:23: "Jesus replied, ‘If anyone loves Me, he will obey My teaching. My Father will love him, and We will come to him and make Our home with him.'"
1 John 3:24: "Those Who obey His commands live in Him, and He in them. And this is how we know that He lives in us: We know it by the Spirit He gave us."
