No, a true believer cannot commit the sin unto death; they are kept by God's grace.
According to 1 John 5:18, those who are born of God do not commit sin. This statement underscores the theological doctrine that true believers are preserved by the grace of God. The sin unto death relates to a complete and willful rejection of Christ and His sacrifice, which cannot occur in a heart truly transformed by the Holy Spirit. True believers may fall into sin temporarily, but they will ultimately be restored because God actively works to keep them from abandoning their faith. The robust guarantee of perseverance is found in the doctrine of the perseverance of the saints, whereby God ensures that none of His chosen will be lost. 1 John 2:19 highlights that those who leave the faith were never truly part of the church, because genuine faith endures.
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