Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins

Acts 2:37-47

When the people heard this, they were cut to the heart and said to Peter and the other apostles, “Brothers, what shall we do?”

Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit. The promise is for you and your children and for all who are far off—for all whom the Lord our God will call.” With many other words he warned them; and he pleaded with them, “Save yourselves from this corrupt  generation.”  Those who accepted his message were baptized, and about three thousand were added to their number that day.

They devoted themselves to the apostles’ teaching and to fellowship, to the breaking of bread and to prayer. Everyone was filled with awe at the many wonders and signs performed by the apostles. All the believers were together and had everything in common. They sold property and possessions to give to anyone who had need. Every day they continued to meet together in the temple courts. They broke bread in their homes and ate together with glad and sincere hearts, praising God and enjoying the favor of all the people. And the Lord added to their number daily those who were being saved.

Why?

Repent and be baptized are the actions Peter answered them the reaction. One day there were 3000 were added to their number.

Those people have the same mind and devoted their own property in common.

For the Holy Spirit with them so the Lord added to their number daily those who were being saved.

How?

It is not our power but is the effort of the Holy Spirit to change the minds of people.