לקח את שמעון ואסר אותו לעיניהם
If ye be true men, let one of your brethren be bound in your prison-house; but go ye, carry corn for the famine of your houses.
Bereishis Rabbah 91:6.
Sefaria · Bereishis Rabbah 91:6
אֲחִיכֶם אֶחָד יֵאָסֵר. הַמִּבְחָן דּוֹרֵשׁ קׇרְבָּן חֶלְקִי, לֹא כְּלִיָּה.
English: Bereishis Rabbah 91:6 explains that Yosef took Shimon and bound him before them, separating him from Levi so they could not conspire together; Shimon then recalls the sale of Yosef.
On the daf / in context: The midrash sees the demand for a single hostage as carefully calibrated pressure that keeps the family intact while forcing them to return with Binyamin.
Type of Learning: Derash on the verse (classic midrash) — not a formal named middah of the 13.
What Is Learned: Yosef’s test is measured; one brother remains as surety while the others are released to bring food and, eventually, Binyamin.