Changing from Base-10 to Base-7 in sefiras haomer

I saw years ago a fascinating idea regarding the counting of sefiras haomer.

The source was discussing the change in counting between the days and the weeks.

We first start counting in base-10: "Today is 15 days"

and then, by counting in relation to the weeks, we effectively switch to base-7: "...which is 2 weeks and one day of the omer." (Sefardim mention the omer between the days and the weeks, but the concept is still the same.)

I remember the book (it was an English sefer) was discussing the concept of going from 10 to 7; I think it had something to do with the sefiros, which we sometimes count as 7 and sometimes as 10 (depending if you count chochma bina and daas/keser or not).

Does anyone know:

1) the English sefer which discusses this?

2) an earlier source for this concept, presumably from where the sefer was coming? (maharal, rav tzadok, etc.)

3) What is the concept of this transition from 10 to 7, and why is it significant specifically when discussing sefiras haomer? I've tried working it out but I don't have any clear explanation.

While searching for this topic I came across some works discussing the difference between counting days and weeks (see here and here)

but I didn't find any discussion specifically about the sefiros transitioning between base-10 and base-7.

A possible haschalas devarim:

At the bris bein ha'besarim it says:

וַיֹּאמֶר לְאַבְרָם יָדֹעַ תֵּדַע כִּי גֵר יִהְיֶה זַרְעֲךָ בְּאֶרֶץ לֹא לָהֶם וַעֲבָדוּם וְעִנּוּ אֹתָם אַרְבַּע מֵאוֹת שָׁנָה.

...

וְדוֹר רְבִיעִי יָשׁוּבוּ הֵנָּה כִּי לֹא שָׁלֵם עֲו‍ֹן הָאֱמֹרִי עַד הֵנָּה.

The Torah initially measures time in years (400 years) and then measures time in generations (the 4th generation).

Rav Hutner quotes the Gr"a as saying

תלה את הקלקול במשך הזמן והתיקון במשך הדורות

Which seems to indicate that the world by itself tends to wither and become disorientated, but people can work and reverse this trend.

Me'inyan le'inyan be'oso inyan...

Maybe we first count the number of days in decimal, which is a scientific/artificial type of counting system. Then we count the number of days in base 7, because the week is a function of the cycle of tikkun and rest (i.e. base 7 is how we count the days, in a human manner). In this way, we mentally transform the natural passage of time (משך הזמן) into an avodah-centric passage of time.

However, this idea (if cogent) would possibly seem to be the opposite of what you are suggesting, because the 10 sephiros include the higher sephiros (whose tikkun is not accessible to us in our current state), as opposed to the 7 lower sephiros (which are accessible to us now, and which is why we only conquered 7 peoples in Eretz Canaan and not 10), according to which going from base 10 to base 7 is going from a higher system to a lower system.

Maybe this is not contradictory, because certain aspects of the world only appear to us as artificial (currently) because we do not have access to the penimiyus of these things. Therefore, rephrased, the above could be stated as: The purpose of changing from base 10 to base 7, is to draw the inaccessible into the accessible.

• This is a beautiful concept. Where does Rav hutner quote the Gra? Also, just to clarify: These are two separate ideas? i.e. Nature leads to kilkul and people can reverse it, and also going from inaccessible to accessible? Or are you connecting the two ideas? – Binyomin Sep 13 '20 at 14:44