Hidden light revealed through mitzvos

במדרש אור זרוע לצדיק כו'.

In the Midrash: "Light is sown for the tzaddik" (Tehillim 97:11) …

The Midrash opens with the verse that a special light is stored away for the righteous, the theme the Sefas Emes will develop here.

דכתיב והארץ היתה תהו כו'.

As it is written, "And the earth was tohu (formlessness) …" (Bereishis 1:2).

He turns to the verse describing the world's primordial state before the light was created.

הם ד' יסודות אשר העולם מורכב מהם תוהו ובהו חושך ורוח כו'.

These are the four elements (yesodos) from which the world is composed: tohu and bohu, darkness and wind.

The four terms in the verse — formlessness, void, darkness, and wind — correspond to the four fundamental elements out of which the physical world is built.

ויאמר אלקים יהי אור.

"And Hashem said, Let there be light" (Bereishis 1:3).

Into this dark, elemental world Hashem introduced light.

אמרו חז"ל שאור הי' מאיר מסוף העולם ועד סופו.

Chazal said that this light shone from one end of the world to the other.

The original light of Creation was not an ordinary light; it illuminated the entire span of the world.

פירוש אור שאין העולם וגשמיות הטבע יכול להסתירו והי' מאיר תוך כל הד' יסודות אך מפני הרשעים גנזו כמ"ש חז"ל.

The meaning is a light that the world and the physical nature cannot conceal, which shone within all four elements; but on account of the wicked, He hid it away, as Chazal said.

This hidden light (ohr haganuz) is a spiritual light that physical nature cannot obscure; it penetrated even the coarse elements. Yet because the wicked were unworthy of it, Hashem concealed it for the tzaddikim.

וע"י המצות שנתן הקב"ה לבנ"י בכל דבר מאיר להם המצוה מעין אור הגנוז וזה הרמז על ד' כנפות כנף הוא התאספות כי כל יסוד הוא שורש להענפים רבים שמתפשטים ממנו והד' ציצית מאירין לכל היסודות בכח אור הגנוז הנ"ל שמאיר מסוף העולם ועד סופו:

And through the mitzvos that Hashem gave to Bnei Yisrael, in each thing the mitzvah radiates to them something of that hidden light. This is the hint of the four corners (kanfos) — "kanaf" connotes a gathering — for each element is a root for the many branches that spread out from it, and the four tzitzis illuminate all the elements with the power of the aforementioned hidden light that shines from one end of the world to the other.

The mitzvos restore access to the hidden light: each mitzvah reveals a glimmer of it. The four corners of the tzitzis correspond to the four root elements (the word "kanaf" implies gathering-in), and through the tzitzis that hidden light is drawn back into all of creation, shining once more across the whole world.

Summary: The light of the first day of Creation shone from end to end of the world, penetrating even the four coarse elements, but it was hidden away because of the wicked. Through the mitzvos, and specifically the four tzitzis corresponding to the four root elements, Bnei Yisrael draw out a glimmer of that hidden light and let it shine once more throughout creation.