What does John 15:17 mean?

For the third time in this discourse, Jesus refers to the Christian obligation to love others (John 13:34; 15:12). This is given an extremely high standard (John 15:12) and involves a very practical approach. Part of Jesus' teaching here is that His followers are not "above" Him (John 13:16). Christ lived out an example of humble service (John 13:12–13). Therefore, anyone who claims to be a Christian ought to be humble and loving towards other people (John 13:34–35), and especially towards other Christians (1 John 4:20–21).

Jesus has also tied the concepts of obedience and love together. He made it clear that those who truly love Him will naturally follow His teachings (John 14:15; 15:14). Christians can and do succumb to sin, at times (1 John 1:9–10). However, the normal, expected pattern of a person's life says a great deal about their relationship to Christ. Those who obey, and bear spiritual fruit, give evidence that they have been saved and are connected to the "True Vine" (John 15:1, 4). Those who do not obey are giving evidence they're only "around" the truth, not a part of it (John 15:2).