Jesus had used the identical words in Revelation 22:7 and Revelation 22:12. By repeating the words now, he places the warning of Revelation 22:18–19 into the context of his return, an event that will come with judgment and the dispensing of fitting rewards (recall Revelation 22:12). With the addition of the word surely,
Jesus strengthens his promise to return soon.
20 He who testifies to these things says, “Surely I am coming soon.” Amen. Come, Lord Jesus!