But encourage one another day after day, as long as it is still called 'Today,' lest any one of you be hardened by the deceitfulness of sin. You can take the most hardened criminal and trace his life back to a point in time when he was not hardened, a time when he was laughing and playing with other children and gave no impression of being hardened. That we why we say the word also suggests a process. First there is the resistance against being thought of as childish. According to the verse we are considering, it has to do with the deceitfulness of sin.
Sin has the power to deceive.
It always promises what it cannot produce. Sin always promises pleasure and satisfaction. In the end it produces untold misery in this life and in the life to come. Sin always ends up costing more than what one intends to pay. Think of those who have paid the price of the loss of their moral integrity, or the loss of their life or the life of a loved one because of indulging in some momentary pleasure.