Unique and Mandatory Salvation
This sentence comes at the end of Peter's defence before the same religious court which previously sentenced Jesus to death. Even though Peter and John had just spent a night in the jail (Acts 4:3), the apostle spoke boldly without any fear for his own life. He was filled with the Holy Spirit and able to speak freely about Jesus, whatever the consequences (Acts 4:8).
The Jews expected salvation to come from God's Messiah ('Christ' is the Greek word). They were right: His Name is Jesus. There is no other God-authorised Saviour (John 14:6), because nobody else could, would or did accept God's punishment for sins, which each of us deserve. Salvation through Jesus is God's plan to rescue rebellious sinners from hell: there is no other plan, no other way, no other saviour (1 Timothy 2:5).
We are saved when we believe in Jesus, repent of our sins and receive the Holy Spirit (Acts 2:38). We cannot save ourselves, Jesus does that (Ephesians 2:8-9). We cannot give ourselves eternal life, the Holy Spirit does that. We cannot generate love in God's heart by doing good, the Father already loves us. But God will not repent for us, we have to do that. To believe, repent and be baptised is not a religious or cultural option for some people; it is a command (1 Thessalonians 5:9). We 'must be saved'. Paul said the same in Acts 17:30, "In the past God overlooked such ignorance, but now he commands all people everywhere to repent." It follows that a refusal to repent is the ultimate rebellion, throwing away God's offer of salvation, and exposing the rebel to the intensity of God's wrath (Romans 2:4-6).
Salvation from God's wrath against sin is only possible because Jesus has already been punished for the sins of the world (1 John 2:1-2). That is why we must believe in Him: there is no other eternally secure option, whatever background we may have come from. It is also why we must tell people that Father God commands them to be saved through Jesus. It is God's message and so we need to let His Holy Spirit give us the words. Ask the Lord for boldness and clarity (Ephesians 6:19-20). Pray that He will speak through you, so that others will believe, repent and receive His new life.