Parsha Mitzvot: Vayikra: Mitzvah 129 – Concept 362
“But if his means are insufficient for two turtledoves or for two young doves, then he shall bring as his guilt-offering for that which he sinned, a tenth-eiphah of fine flour for a sin-offering; he shall not place oil on it nor shall he put frankincense on it, for it is a sin-offering (Vayikra 5:11).” We are forbidden to place oil on the meal-offering of wrongdoers (Rambam, Hilchot Ma’aseh ha-Korbanot – The Laws of the Sacrificial Procedure).
Our natural tendency when making an offering to God, even though we are taught that, “Whether one gives a lot or a little, it is equal before God as long as his heart is directed toward Heaven,” to want to beautify our gift, enhance it just a bit. It is a drive to expand what we are giving. However, this sinner may not add anything to his offering, as he must acknowledge that his sin was against real and lasting expansion. He must hold himself back to experience the constriction of sin. (Service of God Notebooks)