Chasidut zu Wajikra 4:27

‎It is also possible to understand Leviticus 4,27 in a similar sense ‎where the Torah describes the commission of a sin in a peculiar ‎way by writing: ‎נפש כי תחטא....בעשותה אחת ממצות ה' אשר לא ‏תעשינה‎, “when a person commits a sin through performing one of ‎G’d’s commandments which should not be performed.” What is ‎meant is that “someone sins by the manner in which he performs ‎a commandment, i.e. giving himself credit for performance, an ‎act of arrogance.” In other words: we must guard against being ‎smug about our level of service to the Lord. It is described as: ‎ואשם‎, he became guilty.‎We can also say that this is what our sages had in mind in ‎‎Sukkah 30 where they derived the rejection of someone’s ‎offering on the altar, the presentation of which was possible only ‎through the prior commission of a sin, from a verse in Isaiah 61,8 ‎the prophet saying that G’d hates a burnt offering which was ‎offered as a result of the donor having first stolen the animal ‎offered, i.e. ‎כי אני ה' אוהב משפט שונא גזל בעולה‎, “for I, the Lord Who ‎loves justice, hates robbery with a burnt offering.”‎
Our author understands the concept of ‎מצוה הבאה בעברה‎, ‎‎“performance of one of G’d’s commandments at the cost of ‎committing a sin,” as the “sin” consisting of the smugness of the ‎party concerned about the other commandments he has already ‎performed. Such smugness, i.e. spiritual arrogance, is considered ‎sinful. He considers the verse from Isaiah 61,8 that we quoted ‎above as referring to this kind of sin. Any Jew who considers ‎himself a ‎יש‎, “a somebody,” as a result of his having performed ‎commandments instead of his having acquired a more profound ‎sense of humility, has failed to absorb basic lessons of Judaism. ‎He forgets or forgot that even the strength, physical and moral, ‎to perform these commandments was something granted to us by ‎the Creator; it is not something “homegrown.” ‎