“Why does Paul quote the Law if we’re not under it?”

Explain the blessing through Abraham in Genesis 12. Is that only about Jewish believers or all believers? Why does Paul quote one of the Ten Commandments (in Ephesians 6) if we are not under the Law? How do we identify lies we’re believing and replace them with the truth? What did Jesus mean when He said the thief comes to steal, but that He came to give us life?