Onaah

ויקרא כה,יז וְלֹא תוֹנוּ אִיש אֶּת-עֲמִיתוֹ, וְיָׁרֵאתָׁ מֵאֱלֹהֶּיךָ כִי אֲנִי ה', אֱלֹקֵיכֶּם.
The final letters of the first four words spell שְתוּת (one-sixth). This indicates that the law of one-sixth does not apply until the overcharge or underpayment has reached a sixth of the actual value.