Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 151
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 151, with English translation by Maimonides (Rambam).
לבדוק בסימני חגבים לידע טהור מן הטמא, שנאמר: "אשר לו כרעיים" (ויקרא יא,כא).
To check the signs of grasshoppers in order to know which is kosher and which is not kosher, as [Leviticus 11:21] states: "Those which possess jointed [leg like] extensions...."