Neither Leaven nor Honey
The Kotzker Rabbi commented on the verse: "No meal-offering, which you shall bring to the Lord, shall be made with leaven; for you shall make no leaven, not any honey, smoke as an offering made by fire unto the Lord" (Leviticus 2:11). He said: "In your devotion to the Lord, be neither tasteless like leaven, or too sweet-mannered like honey."
Source: Isach Sarfei Kodesh