לֹא־יַחֲבֹ֥ל רֵחַ֖יִם וָרָ֑כֶב כִּי־נֶ֖פֶשׁ ה֥וּא חֹבֵֽל׃ (ס)
Niemand soll die Mühle oder den oberen Mühlstein nehmen, um zu verpfänden; denn er nimmt einen Mann's Leben zu versprechen.
Rashi on Deuteronomy
לא יחבל NO MAN SHALL TAKE [THE LOWER OR THE UPPER MILLSTONE] AS PLEDGE — i.e. if one comes to demand a pledge through the court for his debt he should not take as a pledge anything by which food is prepared (Bava Metzia 113b, 115a).
Rashbam on Deuteronomy
כי נפש הוא חובל, as per Onkelos, you would deprive the debtor of his source of legitimate income.
Tur HaArokh
לא יחבול רחים ורכב, “he must not take an upper or lower millstone as a pledge;” the Torah abbreviated, failing to tell us who the subject is. He is the creditor, who after the loan is overdue, wants to secure his loan with some collateral. If one wants to view this from an aggadic standpoint, the words as they are fit in with the Torah’s directive for the newly wed husband to devote himself to entertaining his bride; a warning to the groom when performing his marital duties not to behave to his wife as if he were grinding mustard seeds.