As for the oblation of the firstfruits - Rather, As an oblation of firstfruits. The words refer to the leaven and honey mentioned in Leviticus 2:11 which might be offered among the firstfruits and tithes (Deuteronomy 26:2, Deuteronomy 26:12; compare 2 Chronicles 31:5). Honey, being used to produce fermentation, and leaven (or, a small piece of fermented dough) were excluded because fermentation was an apt symbol of the working of corruption in the human heart.
Related Commentaries of Leviticus 2:11
Leviticus 2:11-12
11 No meat offering, which ye shall bring unto the LORD, shall be made with leaven: for ye shall burn no leaven, nor any honey, in any offering of the LORD made by fire.
12 As for the oblation of the firstfruits, ye shall offer them unto the LORD: but they shall not be burntb on the altar for a sweet savour.