It is ever Satan's way to harass and perplex simple souls by means of difficult texts; and, generally speaking, those most troubled by these texts are the very ones to whom they least apply. Matt. 12:31, 32 is a passage often used in this way.
A reference to the analogous passage in Mark 3:22-31 makes it quite clear to whom this awful warning applies; namely, to "the scribes which came down from Jerusalem." Those persistent opponents of divine grace, a grace borne witness to by miracles of divine power, were forced to admit the reality of all that the Lord was doing-"Unclean spirits, when they saw Him, fell down before Him," etc.
A special case had just taken place (Matt. 12:22). A demon had been cast out by the Lord. The Pharisees had seen it; they could not deny it; and yet, rather than acknowledge that the miracle had been wrought by the power of the Spirit of God, they deliberately attribute it to Beelzebub, the prince of the demons. This was an unpardonable blasphemy. Mark 3:30 makes this perfectly clear: "Because they [the scribes and Pharisees] said, He [Christ] hath an unclean spirit." To attribute to Satan what was the manifest work of the Holy Ghost, showed up the incurable wickedness of the religious leaders of that day.
In order to deprive many people of the knowledge and joy of salvation, Satan has often raised the question, Is it possible for one who has done so-and-so to be saved? Let the harassed one triumphantly point to Acts 16:31, and say, It is impossible for one who believes on the Lord Jesus Christ to be lost!