Musar do Przysłów 26:1

This Rabbi has also written concerning the negative commandment not to add לבונה, frankincense, to the עולה ויורד sin-offering (5,11) [as opposed to a מנחה offering. Ed.] of a poor person. He quotes a Baraita in which Rabbi Shimon argues that logic would have dictated that even the baked goods offering of a poor sinner required oil and frankincense as a component. The reason for this is that by allowing the sinner not to add these components he would actually profit when compared with an ordinary person offering a מנחה sacrifice. Why then does the Torah forbid the addition of these components? The reason is because the offering of a sinner should not appear to be luxurious. Rabbi Menachem adds that the absence of beauty and fragrant aroma is an additional incentive for the sinner to try and regain his good standing in the eyes of G–d. When the Torah speaks about לא ישים שמן, instead of לא ישים בה שמן, "no oil must be put over it," instead of "no oil must be mixed with it," this is a hint that the sinner does not deserve that his offering be covered with the most expensive of all liquids. It is an indication that this poor man, whose poverty should have caused him to seek out G–d instead of sinning, does not deserve an עליה, ascent, as would have been indicated by a mere לא יצוק עליה שמן, "that the oil must merely not be poured over the offering. He may not use oil with this offering in any form."