What is the sin unto death? What is the blasphemy of the Holy Spirit?

Many have wondered whether a believer is capable of committing the “unforgivable sin” (Matthew 12:31-32) or the “sin unto death” (1 John 5:16). Both of these refer to unbelief in Jesus or rejection of the Gospel message. Therefore, these warnings are not for believers. We have already received the Gospel, and we are completely forgiven of all our sins (Hebrews 10:14). In addition, we possess eternal life and will never experience spiritual death (John 5:24).