This is right after Saul leaves Damascus and is back in Jerusalem. As he was teaching some with the apostles some Greek speaking Jews tried to kill him. At this point the apostle send him back to his home town of Tarsus. Look what it says in chapter 9 verse 31, "The church then had peace throughout Judea, Galilee, and Samaria, and it became stronger as the believers lived in the fear of the Lord. And with the encouragement of the Holy Spirit, it also grew in numbers."
As they lived in the fear of The Lord. (Not that they were afraid but they revered Him) and they were encouraged by the Holy Spirit and that lead to numbers in the church. It's not by what we do in our own strength it is believing and letting the Holy Spirit guide our heart to make us change. When we can do things in our own strength we are not living by faith but our own will. We must let go and let God so as the Holy Spirit encourages us we know that it is Him. Peter goes on to share this in Acts about faith and it is important for us to remember.
Acts chapter 10 verses 34-36 "Then Peter replied, “I see very clearly that God shows no favoritism. In every nation he accepts those who fear him and do what is right. This is the message of Good News for the people of Israel—that there is peace with God through Jesus Christ, who is Lord of all." As we grow and Jesus perfects our faith we have peace in our lives because we can feel the encouragement of the Holy Spirit. Then we move because we are not relying on our own strength. We need to keep focused, keep reading and keep praying so we continue to grow and have peace in The Lord. Amen