We become children of God when we accept Jesus as our Lord and Savior.

(John 1:12 NIV) Yet to all who received him, to those who believed in his name, he gave the right to become children of God--

He quotes Matthew 5:44-45

(Matthew 5:44-45 NIV) But I tell you: Love your enemies and pray for those who persecute you, {45} that you may be sons of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.

We're not saved by doing those things. We do those things because we are saved.