Thank you for the interpretative question on Cornelius’ conversion, “What is the significance of Cornelius’ conversion in the Book of Acts?”
The significance of Cornelius’ vision and conversion is that the Gentiles do not have to be a proselyte Jew in order to receive the gift of salvation from God.
The Acts 10 says this, “Then Peter began to speak: “I now realize how true it is that God does not show favoritism 35 but accepts from every nation the one who fears him and does what is right. 36 You know the message God sent to the people of Israel, announcing the good news of peace through Jesus Christ, who is Lord of all. 37 You know what has happened throughout the province of Judea, beginning in Galilee after the baptism that John preached— 38 how God anointed Jesus of Nazareth with the Holy Spirit and power, and how he went around doing good and healing all who were under the power of the devil, because God was with him.
39 “We are witnesses of everything he did in the country of the Jews and in Jerusalem. They killed him by hanging him on a cross, 40 but God raised him from the dead on the third day and caused him to be seen. 41 He was not seen by all the people, but by witnesses whom God had already chosen—by us who ate and drank with him after he rose from the dead. 42 He commanded us to preach to the people and to testify that he is the one whom God appointed as judge of the living and the dead. 43 All the prophets testify about him that everyone who believes in him receives forgiveness of sins through his name.”
44 While Peter was still speaking these words, the Holy Spirit came on all who heard the message. 45 The circumcised believers who had come with Peter were astonished that the gift of the Holy Spirit had been poured out even on Gentiles. 46 For they heard them speaking in tongues[b] and praising God. Then Peter said, 47 “Surely no one can stand in the way of their being baptized with water. They have received the Holy Spirit just as we have.” 48 So he ordered that they be baptized in the name of Jesus Christ. Then they asked Peter to stay with them for a few days” (NIV).
one Acts 10–11, here are some thoughts for one’s consideration:
A. Cornelius heard about the message of John the Baptist and the words and works of Jesus.
As a Roman centurion, he was well aware of the events in Israel in case there was any revolt. He received reports about John the Baptist and Jesus of Nazareth.
“36 You know the message God sent to the people of Israel, announcing the good news of peace through Jesus Christ, who is Lord of all. 37 You know what has happened throughout the province of Judea, beginning in Galilee after the baptism that John preached— 38 how God anointed Jesus of Nazareth with the Holy Spirit and power, and how he went around doing good and healing all who were under the power of the devil, because God was with him” (NIV).
Cornelius received reports that he heard from the Roman soldiers of John the Baptist and of Jesus of Nazareth. It was his responsibility to know about gatherings of people for possible revolt. With the multitude of people gathering to here John and Jesus, Cornelius watched the people closely.
B. Cornelius believed in God but had an inadequate understanding for salvation.
Cornelius read the reports or perhaps even heard the words of John the Baptist or Jesus when he preached by the Sea of Galilee. He heard reports from a royal official that Jesus healed his son. He may have believed that Jesus was a prophet of God but he didn’t know or understand that Jesus is the Son of God, the Savior of the world.
C. Cornelius received a vision so that he can hear the forgiveness of sins without having to be a proselyte Jew.
Acts 10 says this, “34 Then Peter began to speak: “I now realize how true it is that God does not show favoritism 35 but accepts from every nation the one who fears him and does what is right. 36 You know the message God sent to the people of Israel, announcing the good news of peace through Jesus Christ, who is Lord of all. 37 You know what has happened throughout the province of Judea, beginning in Galilee after the baptism that John preached— 38 how God anointed Jesus of Nazareth with the Holy Spirit and power, and how he went around doing good and healing all who were under the power of the devil, because God was with him.
39 “We are witnesses of everything he did in the country of the Jews and in Jerusalem. They killed him by hanging him on a cross, 40 but God raised him from the dead on the third day and caused him to be seen. 41 He was not seen by all the people, but by witnesses whom God had already chosen—by us who ate and drank with him after he rose from the dead. 42 He commanded us to preach to the people and to testify that he is the one whom God appointed as judge of the living and the dead. 43 All the prophets testify about him that everyone who believes in him receives forgiveness of sins through his name.”
44 While Peter was still speaking these words, the Holy Spirit came on all who heard the message. 45 The circumcised believers who had come with Peter were astonished that the gift of the Holy Spirit had been poured out even on Gentiles. 46 For they heard them speaking in tongues[b] and praising God. Then Peter said, 47 “Surely no one can stand in the way of their being baptized with water. They have received the Holy Spirit just as we have.” 48 So he ordered that they be baptized in the name of Jesus Christ. Then they asked Peter to stay with them for a few days” (NIV).
The central point and significance of Cornelius, being a Gentile, is that salvation is granted by faith to whoever believes without any religious requirements. The proof for the Apostle Peter is that the Holy Spirit came upon them as they believed his message by the sign of speaking in tongues, not that they have to follow any Jewish rituals.
SUMMARY: Salvation is a gift of God, apart from human works or church rules, that is received by faith and faith alone.
For more perspectives:
https://www.quora.com/What-is-the-significance-of-Cornelius-conversion-in-the-Book-of-Acts