I believe that the Pauline Epistles, so with the books of Peter and John their recipients are believers. Is there a verse that Paul in his letter to Ephesians, especially in his prayer in Eph. 3:14-19, he was talking to unbeliever? "that Christ may dwell in your hearts through faith"
Ephesians 3:14[NIV] For this reason I kneel before the Father, 15 from whom every family[a] in heaven and on earth derives its name. 16 I pray that out of his glorious riches he may strengthen you with power through his Spirit in your inner being, 17 so that Christ may dwell in your hearts through faith. And I pray that you, being rooted and established in love, 18 may have power, together with all the Lord’s holy people, to grasp how wide and long and high and deep is the love of Christ, 19 and to know this love that surpasses knowledge—that you may be filled to the measure of all the fullness of God.