18 "If the world hates you, you know that it hated Me before it hated you.
19 If you were of the world, the world would love its own. Yet because you are not of the world, but I chose you out of the world, therefore the world hates you.
20 Remember the word that I said to you, 'A servant is not greater than his master.' If they persecuted Me, they will also persecute you. If they kept My word, they will keep yours also.
21 But all these things they will do to you for My name's sake, because they do not know Him who sent Me."
world (v.18) — the order and system of humanity.
Believers are not of this world (v.19) because they have been born of the Spirit and possess a divine nature. The believers' separation from the world condemns those in the world by contrast.
To persecute believers (v.20) is to persecute Christ (Acts 9:4). This shows the believers' unity with Christ — and the disciples words were the words of Christ.
Christ was preparing the disciples for the persecution they would face after His departure. Until that time, they were not persecuted (Luke 10:17; John 18:8).
The more Christlike we are, the more persecution we will face.