There is difference between unbelief, transgression and disobedience.
There is difference between unbelief, transgression and disobedience. Unbelief means denial. Like one says, “O gentlemen! These things are now outdated and old. Now man has conquered space and is planning to colonize the moon.” In a way you are mocking by saying, “What is this all about the first night in the grave?” Unbelief means denial of the origin and end (of man). Transgression means sinning. It is not as adverse as disbelief.
A transgressor does not deny and mock Allah and Judgment Day, accounting, heaven and hell. Rather he believes in them. Yet he becomes a bully and a ruffian. When he is asked, “Why do you not observe fast?” He replies, “My heart is not inclined to it.” He turns his head and replies, “Why should God need my or your fasting?” This is transgression. It is getting out of obedience, stepping out of God worship. He does not imagine himself to be a servant. Below this offence is disobedience.
Some have said that transgression means greater sins especially falsehood, but disobedience is any type of sin, greater or smaller. Summarily, A pious believer is one who loves God, abhors disbelief, transgression and disobedience. Not the disobedience of people, but disobedience of his own self also. He dislikes obscenity and immorality. A true believer is one who dislikes abuse from the viewpoint that it, in itself, is bad, not because he has been abused.
(49:7)” It is these who are rightly guided and perfectly faithful. He is a true and good believer who dislikes every sin, offence and indecency. Neither every believer becomes like this nor does every Muslim reach this position. Maybe there is only one in a thousand who is such.