ויחפש בגדול החל ובקטן כלה ולמה עבד כן שלא יאמרו יודע היה היכן הוא מונח
Then they hastened, and took down every man his sack to the ground, and opened every man his sack.
Bereishis Rabbah 92:8.
Sefaria · Bereishis Rabbah 92:8
וַיְמַהֲרוּ וַיּוֹרִדוּ... וַיִּפְתְּחוּ. הַזְּרִיזוּת מְעִידָה עַל בִּטָּחוֹן בְּחַפּוֹתָם.
English: Bereishis Rabbah 92:8 explains that the search began with the eldest and ended with the youngest so the brothers would not suspect that Yosef’s household already knew where the cup had been placed.
On the daf / in context: The midrash observes that the brothers’ rapid compliance with the search is the behavior of men who are certain nothing will be found.
Type of Learning: Derash on the verse (classic midrash) — not a formal named middah of the 13.
What Is Learned: The brothers open their sacks willingly and quickly because they know themselves to be clean; the discovery that follows is therefore all the more devastating.