(condensed from Ein Ayah, Shabbat 1:53)Gemara:
[The Rabbis said not to read by the light of an oil lamp, but some thought that it was permitted for a person who knows how to be careful
]. … [He] read and tilted the oil lamp and wrote in his notebook: "I, [Yishmael ben Elisha] read and tilted the lamp on Shabbat; when the Beit Hamikdash will be built, I will bring a fat sin offering." Ein Ayah:
Writing in a notebook awakens a person to realize it is proper to remember, not forget, one’s sins. If all acts of sin would only have a temporary impact on one’s soul, it would have sufficed for him to repent at the time of the sin, rendering remembering the sin long term superfluous. In truth, though, a person’s spiritual powers and his personal actions are intertwined, and one sin can ruin much goodness. Each act of sin has a negative impact on several of a person’s good attributes and can cast away a person’s altruism from his heart, according to the level of the sin and the imprint it leaves.
A person’s spiritual powers are hidden, and some of their shortcomings are unnoticeable except when life arranges matters so that he needs to act by using that power, which he will then find to be lacking. Only at that time will the person be able to rectify the shortcoming by having the powers of goodness and sanctity, which are the foundations of repentance, overcome and thereby fix the shortcoming.
For this reason, a person should make sure that his sin will not be forgotten until he sees that his spiritual powers that relate to the area of the sin are complete and are not harmed either in attributes or in philosophies. Then he can be happy and know reliably that his sin has left him and has dissipated like a cloud.
Every action makes a different imprint on the soul, not just according to its value as good or evil, but also based on the situation and reasons that caused it. One cannot compare, for example, the impact of an action that was done when a person was in a good mood to one performed when in a state of heartache. It takes great study to know how to strengthen the position of goodness and sanctity in a person’s soul in relation to the damage that sin brought according to the essence of the sin and its circumstances. Therefore one should not only write down the essence of the sin but even the factors that brought it about. That is why Rabbi Yishmael ben Elisha wrote that he was reading (the cause) and tilted the lamp (the action), stressing the noteworthiness not only of the action but even its causes.
The human body lives and survives with the help of its flesh and bones. The body’s fat provides some benefit that would otherwise be missing. Sin also is supported by factors that help bring about the sin. If a sin’s causes did not make a difference, then the fatness of the sacrifice brought to atone for it would not be significant enough to record and remember. Rabbi Yishmael realized that he needed to distance himself greatly from the decision to not heed the warning of the Rabbis. Therefore the fact that he decided to read by the light of the lamp had to be written with the fact that he needed atonement, even though the sin (violating Shabbat) has its own complete character without this specific cause. He also recorded the need to bring a fat animal to stress that he needed atonement for that which made the sin a "complete one," as his thought process was intrinsically lacking and required work. Every person needs to learn from this story and be vigilant to follow all of the injunctions of the Rabbis, without trying to find personal ways around them. Therefore, the circumstances that surrounded the sin needed to be recorded as part of the effort to receive full atonement.