If you are born once, you will die twice. If you are born twice, you will die once. By "born once," I mean the physical birth. By "born twice," I mean a physical birth as well as a spiritual birth in which you are born again, spiritually putting your faith in Christ. Just as there are two births, the Bible teaches there are two deaths: one is physical, and the other is spiritual. Jesus warned that we are to fear the second death more than the first one.
Romans 10:9-13
9 That if you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved.
10 For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved.
11 As the Scripture says, "Anyone who trusts in him will never be put to shame."
12 For there is no difference between Jew and Gentile--the same Lord is Lord of all and richly blesses all who call on him,
13 for, "Everyone who calls on the name of the Lord will be saved."