Mutual longing in Creation

במדרש שוקיו זה העולם שנשתוקק הקב"ה לבראתו שכן נאמר ויכלו כו' לשון תאוה.

In the Midrash: "His thighs (shokav)" — this refers to the world that the Holy One, blessed is He, desired (nishtokeik) to create, as it is said, "And they were completed (vayechulu)…" — an expression of longing.

The Midrash plays on the similarity between shokav (thighs) and the root of teshukah (desire/longing): the world is something Hashem longed to bring into being, and even the word vayechulu hints at that yearning.

אעפ"י שזה קאי על מעשה בראשית והמד' אמר על תשוקת הבורא ית' כמ"ש ועלי תשוקתו.

Even though this verse refers to Maaseh Bereishis (the work of Creation), the Midrash applies it to the longing of the Creator, may He be blessed, as it is written, "and toward Me is his longing (ve'alai teshukaso)."

The Sefas Emes notes the apparent difficulty: the pasuk speaks of the completion of Creation, yet the Midrash reads it as Hashem's own desire — and brings the verse from Shir HaShirim that speaks of a mutual longing.

אכן ביאור הדברים שביד התחתונים לעורר רצון הבורא ית' כמ"ש ויכלו כו' אח"כ כתיב ויכל אלקים כו' וז"ש ועלי תשוקתו שתשוקת הבורא ית' תלוי ברצון ותשוקת תחתונים לדבקה בו:

Rather, the explanation is that it lies in the power of those below to awaken the ratzon (will) of the Creator, may He be blessed — as it is written "vayechulu (and they were completed)," and afterward it is written "vayechal Elokim (and Hashem completed)…" — and this is the meaning of "ve'alai teshukaso," that the longing of the Creator depends upon the will and longing of those below to cling to Him.

The resolution: Hashem deliberately made His own "desire" for the world contingent on our desire for Him. First "vayechulu" — the world is, as it were, completed by the yearning that rises from below; only then "vayechal Elokim" — Hashem brings it to completion. So Hashem's teshukah is awakened by the teshukah of Bnei Yisrael who long to be deveikus (cleave) to Him.

Summary: The world is rooted in a mutual longing. Hashem desired to create it, yet He made His own longing depend on the longing of those below — when Bnei Yisrael yearn to cleave to Hashem, they awaken His ratzon, so that the completion of Creation flows from the desire that rises from below.