What does Acts 3:15 mean?

Peter is explaining to a crowd of Jews that they—like all people of all nations—are responsible for the death of the Holy One whom God sent.

"Author" is from the Greek root word archēgos and has the double-meaning of both originator and leader; in the New American Standard Bible, it is translated "Prince." Jesus is the originator of life; John 1:3 says of Him, "All things were made through him, and without him was not any thing made that was made." He also maintains creation: "And he is before all things, and in him all things hold together" (Colossians 1:17). Jesus is also ultimately the ruler of creation: "King of kings and Lord of lords" (Revelation 19:16).

It's significant that the Bible states God raised Jesus from the dead (Galatians 1:1); Jesus did not raise Himself. Jesus died as an act of submission to God and God's plan (Philippians 2:5–8). He submitted to the burden of sin that made God turn His face away (1 Peter 2:24; Mark 15:34). He submitted Himself to death and burial. That God raised Him from the dead proves that He was the perfect, sinless sacrifice who died for the sins of the world (Romans 4:24–25).

Shortly before Jesus ascended into heaven, He told His disciples they would be His witnesses "in Jerusalem and in all Judea and Samaria, and to the end of the earth" (Acts 1:8). "Witness" is from the Greek root word martys. As witnesses, the disciples gave first-hand testimony about Jesus' life, death, and resurrection. But as persecution against the church rose, martys took on a different meaning and is now the base of our word "martyr." A witness in this context, then, is someone who will speak the truth about Jesus, even at the expense of their own life. Church tradition says that all of the apostles, except John, died as martyrs.