This week’s parsha makes it perfectly why this book is commonly referred to in English as Numbers. After counting all of B’nei Yisrael, Moshe is instructed to conduct a ceremonial swap of first-born for Levi’im, a procedure signifying the consecration of the the descendants of Levi as the performers of the service of HaShem, a position previously held by the first-born. First, Moshe counts up all of the Levi’im and the Torah (3:39) reports a total of 22000. The first-born are subsequently counted and their total is 22273. The procedure for the extra 273 does not concern us for now. What is of importance is the point made by Rashi on the tally of the Levi’im. If you add up the figures that the Torah gives us – 7500 for Gershon, 8600 for Kehas and 6200 for Merari – you get a total of 22300!! That would have avoided the need for a special procedure for the extra 273. However, Rashi tells us, based on the gemara (Bechoros 5a) that those 300 extra Levi’im were first-born themselves and therefore, they redeemed themselves, so to speak, and could not be used to redeem other first-born.
Ibn Ezra quotes a complicated calculation from Yehudah HaParsi (whom I believe was a Kaarite,) which he then proceeds to take apart. This is how I, with the help of a friend and the sefer Be’er Yitzchok, understood the give and take in the Ibn Ezra:
Yehudah HaParsi attempts to show how Chazal’s “assumption” that the 300 uncounted Levi’im were in fact first-born is a mathematically sound one. The proposed number of first-born of the Levi’im, three hundred, is approximately 1/73 the size of the general Levite population of 22000. The first-born among the rest of B’nei Yisroel, 22273, were 1/27 the size of the general population. The proportions seem way off at first glance. However, there is one catch. The general population was counted from 20 years old and up. But the first-born were counted from one month and up. Of the Levi’im, however, both the general population and the first-born were counted from one month.
Yehudah HaParsi proposes the following adjustment: Beginning at the end of this week’s parsha and spilling over into next week’s, the Levi’im of the age of service are counted. The total given (4:48) is 8580. Subtracting the 300 first-born, we are left with 8280. The Levi’im of the age of service therefore make up a mere 38% of the total Levite population (8280/22000=0.38). If we were to take only that percentage of the first-born of the rest of B’nei Yisroel, there would be only 8383 first-born of the age of service ((8280/22000)*22273=8383). This is remarkably 1/73 of the general population of B’nei Yisroel which was initially tallied based on service age, an astonishingly accurate correlation with the Levite figure of 1/73. This is truly a brilliant calculation.
However, Ibn Ezra didn’t think so. He strikes down the entire calculation with one very simple fact that I deliberately avoided exposing until now. The age of service for the Levi’im was from 30 to 50. The counting of B’nei Yisroel began at 20 years old without any upper bound. Thus, there is no rationale for comparing the two figures. [There are other mathematical flaws as well. It is foolish to subtract all 300 first-born Levi’im from 8580. Either the first-born should be subtracted proportionately (117) or the 8580 should simply be divided by 22300, ultimately resulting in 1/71 as the proportion of regular first-born.] Rather than trying to come up for some “proof” for the validity of the words of Chazal, we must accept them as truth with full faith that that is what was passed on to them.