וא"ר יצחק אין הברכה מצוייה אלא בדבר הסמוי מן העין שנאמר (דברים כח, ח) יצו ה' אתך את הברכה באסמיך תנא דבי רבי ישמעאל אין הברכה מצויה אלא בדבר שאין העין שולטת בו שנאמר יצו ה' אתך את הברכה באסמיך ת"ר ההולך למוד את גורנו אומר יהי רצון מלפניך ה' אלהינו שתשלח ברכה במעשה ידינו התחיל למוד אומר ברוך השולח ברכה בכרי הזה מדד ואח"כ בירך הרי זה תפילת שוא לפי שאין הברכה מצוייה לא בדבר השקול ולא בדבר המדוד ולא בדבר המנוי אלא בדבר הסמוי מן העין שנאמר יצו ה' אתך את הברכה באסמיך
Rabbi Yitzḥak says: Blessing is found only in a matter concealed from the eye, as it is stated: “The Lord will command blessing with you in your storehouses” (Deuteronomy 28:8), where the grain is concealed. The school of Rabbi Yishmael taught: Blessing is found only in a matter over which the eye has no dominion, as it is stated: “The Lord will command blessing with you in your storehouses.” The Sages taught: One who goes to measure the grain on his threshing floor recites: May it be Your will, O Lord, our God, that You send blessing upon the product of our hands. If one began to measure the grain he says: Blessed is He Who sends blessing upon this pile of grain. If one measured and afterward recited this blessing, this is a prayer made in vain, because blessing is found neither in a matter that is weighed, nor in a matter that is measured, nor in a matter that is counted. Rather, it is found in a matter concealed from the eye, as it is stated: “The Lord will command blessing with you in your storehouses.”
(ד) וְלָמָּה מוֹנֶה הַמִּנְיָן שֶׁהִסְכִּימוּ עָלָיו עַל הָאֶצְבָּעוֹת שֶׁהוֹצִיאוּ וְלֹא הָיָה מוֹנֶה עַל הָאֲנָשִׁים עַצְמָן לְפִי שֶׁאָסוּר לִמְנוֹת יִשְׂרָאֵל אֶלָּא עַל יְדֵי דָּבָר אַחֵר שֶׁנֶּאֱמַר (שמואל א טו ד) "וַיִּפְקְדֵם בַּטְּלָאִים":
(4) Why was the number agreed upon counted on the thrust-out fingers and not on the individuals themselves? Because it is forbidden to count Israelites except by means of some other object, as it is written: "He numbered them by sheep" (I Samuel 15:4).
"Not one, not two, not three, not four.."
The custom in Yiddish of counting negatively - nit ein, nit zwei - has deep roots in Jewish culture and consciousness. A fear of numbering prompts us to be circumspect. And I would dare to say that for Jews demography is not a value-free science. Our numbers are too small to be carefree or indifferent. For a vulnerable minority counting is always a matter of gravity. We know our vital statistics all too well...The number of six million is forever etched in Jewish memory. In truth, we never came close to becoming as innumerable as the stars. Exile is a precarious terrain, so despite our secular temperament, we relate to population surveys with foreboding. The paucity in our numbers drives us to take comfort in the profusion of quality, which we should, for never have so few influenced so many. Therein lies the fulfillment of God's promise to Abraham that his seed will be a blessing to all humanity (Gen 18:18).
Ismar Schorsch, 5762