Mark 3:29

3:29 But whoever blasphemes against the Holy Spirit will never be forgiven, but is guilty of an eternal sin” ¹ 

Mark 4:12

4:12 so that although they look they may look but not see,

and although they hear they may hear but not understand,

so they may not repent and be forgiven.” ² 

[3:29]  ¹ sn Is guilty of an eternal sin. This passage has troubled many people, who have wondered whether or not they have committed this eternal sin. Three things must be kept in mind: (1) the nature of the sin is to ascribe what is the obvious work of the Holy Spirit (e.g., releasing people from Satan’s power) to Satan himself; (2) it is not simply a momentary doubt or sinful attitude, but is indeed a settled condition which opposes the Spirit’s work, as typified by the religious leaders who opposed Jesus; and (3) a person who is concerned about it has probably never committed this sin, for those who commit it here (i.e., the religious leaders) are not in the least concerned about Jesus’ warning. On this last point see W. W. Wessel, “Mark,” EBC 8:645-46.

[4:12]  ² sn A quotation from Isa 6:9-10. Thus parables both conceal or reveal depending on whether one is open to hearing what they teach.