Avraham mended the world's garment

במדרש אחות לנו זה אברהם שאיחה כל העולם כזה שמאחה את הקרע כי כל הבריאה הוא מלבוש להפנימיות ואם עובד ה' מתקן כל דבר לאמיתו ומדבקו בשרשו ויודע להעמיד כל דבר על מקומו ונגמר המלבוש אז שורה בו הפנימיות כדמיון הלבוש שהוא נעשה ע"י איחוי וחיבור חתיכות בגד כן כל עניני עוה"ז אינם מסודרין כמ"ש גם את העולם כו' מבלי אשר ימצא כו' מראש עד סוף.

In the Midrash, "We have a sister" (Shir HaShirim 8:8) — this is Avraham, who stitched together (ichah) the whole world, like one who mends a tear; for all of creation is a garment (malbush) for the penimiyus (inner dimension), and if one serves Hashem he repairs each thing to its truth and binds it to its root, and knows how to set each thing in its place, and the garment is completed — then the penimiyus rests within it, in the likeness of a garment, which is made by stitching and joining pieces of cloth; so too all the matters of this world are unordered, as it is written, "also the world… without a man being able to find out… from beginning to end" (Koheles 3:11).

Avraham is called the one who "mended the tear" of the world: creation is merely an outer garment concealing an inner divine essence, and the avodah of serving Hashem is to repair each scattered thing, restore it to its true place, and bind it to its root — only then is the "garment" whole and able to host the inner light, just as a garment is sewn from separate pieces of cloth; on their own the affairs of this world lie disordered and incomprehensible.

רק ע"י מצות ומעש"ט יכולין לתקן הכל:

Only through mitzvos and maasim tovim (good deeds) can one repair everything.

The tool for mending creation's "tear" and assembling the garment is the performance of mitzvos and good deeds, which alone can put every fragment of the world back in its proper place and reveal the penimiyus within it.

Summary: Avraham "mended the tear" of the world by revealing that all of creation is merely an outer garment for an inner divine essence; the avodah of serving Hashem is to repair each disordered thing, bind it to its root, and complete the garment so the penimiyus can rest within — and this mending is accomplished specifically through mitzvos and good deeds.