Witnessing to an atheist
When witnessing to an atheist who questions the resurrection and the authenticity of the Bible, what is the best approach to open their ears to the gospel?
I can suggest that you have your friend read a portion of Scripture like the gospel of John. Since the Holy Spirit alone can change hearts and minds, do what you can to encourage your friend to read the Scriptures and let God speak for himself.
Northwestern Publishing House has some valuable resources that may be of help to you and your friend. This link will take you to the appropriate section of their website.
Finally, continue to pray for your friend. Pray that God would change heart and mind to acknowledge and confess the truths of Scripture: most importantly, that Jesus Christ is Lord and Savior (John 20:31). God bless your witnessing efforts.