Arousal from below precedes the gift of holiness from above

והקדים אחור לקדם שהוא הקדמת עבודת האדם שיהי' אשה מזרעת תחלה.

And He placed "achor" (back) before "kedem" (front) — which is the precedence of man's avodah, that "a woman gives seed first."

The Torah's order in "achor vakedem tzartani" (You formed me back and front) places "back" first, hinting that the human being's effort comes first — paralleled by the halachah that when "the woman gives seed first," the result is altered, symbolizing the primacy of effort from below.

וכן הוא בימי המעשה עבודת הבירור.

And so it is during the six days of work (yemei hamaaseh): the avodah of birur (clarification).

The weekdays are the time for the toilsome avodah of separating good from evil — the human effort that must come first.

וע"ז נאמר והתקדשתם להשתוקק למצוא הקדושה.

And about this it is said, "and you shall sanctify yourselves" (Vayikra 11:44) — to yearn to find the kedushah.

"You shall sanctify yourselves" is a call to the effort of yearning — the avodah of striving from below to reach holiness.

יום הששי ויכלו הוא השתוקקות המקבלים שמזה הטעם אשה מזרעת תחלה יולדת זכר.

"The sixth day, and they were completed (Vayechulu)" (Bereishis 1:31-2:1) is the yearning of the recipients — and for this reason, when "a woman gives seed first, she gives birth to a male."

The sixth day represents the longing of those who receive (an arousal from below); just as the woman's initiative produces a male child, the yearning of the recipients draws down a higher, more "active" kedushah.

והייתם קדושים הוא בחי' יום השבת קדושה הבאה מלמעלה במתנה והוא בחי' קדם.

"And you shall be holy" (Vayikra 11:45) is the aspect of Shabbos — a kedushah that comes from above as a gift, and it is the aspect of "kedem" (front).

In contrast to the active "sanctify yourselves" of the weekdays, "you shall be holy" describes the holiness of Shabbos, which descends from above as an unearned gift — the "front" that follows the "back" of human effort.

וז"ש והייתם בהוויתן יהיו.

And this is the meaning of "and you shall be" (vihiyisem) — "they shall be in their [natural] state of being."

The wording "you shall be" denotes a holiness that simply is — a settled, given state, rather than one achieved through striving.

פי' כשבא ע"י אתערותא דלתתא מקודם אז הוא דבר של קיימא כנ"ל:

The explanation: when it comes through an arousal from below (isarusa diltata) first, then it is something enduring (davar shel kayama), as above.

The gift of holiness from above becomes permanent only when it is preceded by the arousal from below — human effort first earns and anchors the heavenly kedushah, making it lasting.

Summary: The Torah's phrase "achor vakedem" (back and front) teaches that man's avodah comes first ("back") and the gift from above follows ("front"), mirrored in the principle that when "the woman gives seed first" a male is born. The six weekdays are the time of the avodah of birur and yearning — "sanctify yourselves," an arousal from below — while Shabbos is the holiness that descends from above as a gift, "you shall be holy." The deeper lesson is that the heavenly gift of kedushah becomes enduring (davar shel kayama) precisely when it is first earned through the isarusa diltata, the human effort and yearning from below.