Is he who does not feel guilt sinful?

Lack of guilt, if due to ignorance for which one is excused, such as a new convert to Islam who drinks alcohol unknowingly of its prohibition, then there is no sin upon him. However, if the lack of guilt is despite knowing it is a sin, then it is a sign of belittling the sin, and this in itself is a major sin. Belittling a sin is a sign of a sick heart, and perhaps of hypocrisy, as Ibn Mas'ud said: "And the hypocrite sees his sin like a fly that landed on his nose and then flew away." Furthermore, lack of guilt prevents repentance, which is obligatory, and one of its conditions is remorse. Whoever does not feel remorse for an evil act, it is an indication of their contentment with it and persistence in it. Therefore, it is obligatory for the servant to fear Allah and consider the greatness of the One they have disobeyed, and not to belittle their sin, lest it become a major sin through belittlement.