“I will make your offspring as the dust of the earth so that if one can count the dust of the earth, then your offspring, too, can be counted.”
Rashi comments: Just as it is impossible for the dust to be counted, so your offspring will not be counted.
As Rashi explains, the blessing is that Bnei Yisroel will not be able to be counted, like the dust. Why then doesn’t the posuk write it that way – “just as dust cannot be counted so too your offspring will not be able to be counted”? Why is it written in the positive, thereby implying the opposite of the blessing’s intent?