Musar על פסחים 15:22

When one looks at the letters in the two words חמץ and מצה, one is struck by the fact that though they represent diagonally opposite concepts, the only difference is that the letter ח of the word חמץ appears as slightly imperfect in the guise of the letter ה in the word מצה. Our sages have said that the reason the letter ה has two openings is to give potential penitent sinners an additional opening from the side. To the query why such a penitent sinner cannot simply "enter" from below, they answer that this would not represent an assist to him. The letter ה in the word מצה is therefore seen as an invitation to the בעל תשובה. The letter ח in the word חמץ, is closed off above. This is an allusion to the need to examine one's house for any חמץ before the Passover wherever such חמץ could have entered. When we apply this to our bodies, it means we must examine every limb and organ to ensure it has not been invaded by the evil urge. To illustrate: The mouth has to be examined if it has not been guilty of slander, defamation of character, and all the other abuses of speech we are commonly guilty of.. We also need to check whether the mouth instead of "exporting" something unseemly has not "imported " something forbidden in the way of food and drink. The heart must be examined to see if it has harboured forbidden thoughts and desires. The eyes have to be examined to see whether they have not been guilty of watching and enjoying forbidden sights such as pornography, etc. The best time to conduct such an examination is at night when one is alone and can concentrate on the matter without fear of being distracted. It is best to do all this immediately prior to going to sleep. This is the time to review one's activities and to examine if one has been remiss in some respect. Once one has found such sins, one must "burn" them. Our sages have told us that the most important element of ridding oneself of such חמץ is to eliminate it from one's heart. When a person is truly sorry and approaches G–d with a broken heart his repentance will not be rejected. Our sages arranged that people should also express the destruction or annullment of their חמץ with their mouth; this is why they formulated the short prayer כל חמירא. After having recited this formula one has cleansed oneself spiritually both in thought, in word and in deed. When reviewing one's sins one must search both for sins committed against one's fellow-man as well as for sins committed against G–d directly. I have written more about this in my treatise on מסכת פסחים.