And the reason for this is because the word אם (if) is a word of division. This is not the case with the word כי (when), which is similar to the word כאשר (when), that points out that it is a certainty; thus, it comes at the beginning of the expression and section. And the word אם comes in the particulars of the divisions. And in any place where the word אם comes, there will be a division, an uncertainty, and a possibility.

And when it is written ואם תקריב מנחת ביכורים (And if you bring a meal-offering of first-fruits to the LORD)²⁰⁴, it is peculiar in language, as it should say וכי תקריב. (Since also according to Rabbi Abraham Ben Meir Ibn Ezra, one cannot say that it is divided from the previous statement, because there is a rule that the word which is the foundation of the division is always right after the word אם – whether it is a noun or a verb – as it would have said ואם מנחת ביכורים תקריב.) And the sages of blessed memory explain that the word אם falls on a matter that has in it a possibility from the perspective of time; since in the future, the grain offering might be suspended (through exile) and subsequently be restored, and similarly for the Jubilee Year.

Leviticus 2:14 says,ואם תקריב מנחת בכורים ליהוה אביב קלוי באש גרש כרמל תקריב את מנחת בכוריך(And if you bring a meal-offering of first-fruits to the LORD, you shall bring for the meal-offering of your first-fruits corn in the ear parched with fire, even groats of the fresh ear), using the wordsואם תקריב מנחת ביכוריםfor “And if you bring a meal-offering of first-fruits”. The foundation of the division appears to beמנחת ביכורים*(meal-offering of first-fruits), since various other types of meal-offerings are referred to in Leviticus 2:1-13; hence, it appears that it should have saidואם מנחת ביכורים תקריב. The last sentence of Rule 100 explains otherwise²⁰⁵.*

footnotes: ²⁰⁴ Leviticus 2:14. ²⁰⁵ Malbim, HaTorah ‘HaMitzvah Vayikra 148.