Introduction to the text - Jesus's warning about persecution 

But when the Helper comes, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will bear witness about me. And you also will bear witness, because you have been with me from the beginning.  John 15:26, 27 (ESV) 

Introduction to the sermon - The importance of a good witness

Fallen Condition Focus: Cowardice and timidity keep us from fulfilling our task

Sermon Proposition: Since the Holy Spirit, the Comforter, is sent to us to bear witness, we ought to learn from the Holy Spirit how to testify as witnesses

I. Since the Holy Spirit, the Comforter, is sent to bear witness, we must learn from his testimony given through the apostles about our testimony

1. It is about Jesus' resurrection (Acts 1:22; 2:32)
2. It is about Jesus' identity as the Messiah, the Son of God (John 20:30-31)
3. It is about God's salvation given through Jesus (Acts 2:38-39)

II. Since the Holy Spirit, the Comforter, is sent to bear witness, we must learn how to depend upon the Holy Spirit's grace

1. The Holy Spirit's initiative (Acts 1:8; 2:1-4)
2. The Holy Spirit's words (Acts 2:14-36; Matt. 10:19-20)
3. The Holy Spirit's power (Acts 4:19; 2 Tim. 1:7)
4. The Holy Spirit's wisdom and guidance (Acts 8:4-40)

III. Since the Holy Spirit, the Comforter, is sent to bear witness, we must learn from example of other believers how to be a faithful witness for Jesus

1. As a witness we use our God-given influence to testify
2. As a witness we testify with our words to family, friends, and strangers in friendly and respectful conversation
3. As a witness we testify with our loving acts of service

Conclusion

Jesus is calling his church to serve as his witnesses. He has given us his Holy Spirit to complete our task. Will you and I accept Jesus' call and serve as his witnesses where he has placed us?