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The best way to defend and keep the faith is to preach the gospel. First Corinthians 15:1-4 That Christ died for our sins, according to the scriptures, that He was buried, and rose again on the third day, according to the scriptures.
John 3:16 For God so loved the world, that He gave His only begotten Son, Jesus, that whosoever, believeth in Him, should not perish, but have everlasting life.
We were give two commandments. Believe on the Lord Jesus Christ, and love one another.
Believe on the Lord Jesus Christ, That is our promise of heaven, and Love one another is for rewards. Do unto others as you would have them do unto you.