"And it was, when Israel had sown" (Judges 6:3). Rabbi Huna bar Pappa said: A person should always be careful with the produce inside his house, for Israel were never called poor except over matters of produce, as it is said, "And it was, when Israel had sown, that Midian came up, and Amalek" (Judges 6:3); and it is written, "And Israel was greatly impoverished" (Judges 6:6).
Why a Person Must Guard the Grain Within His House
Yalkut Shimoni on Nach 60:2
והיה אם זרע ישראל. אמר רבי הונא בר פפא לעולם יהא אדם זהיר בתבואה בתוך ביתו שלא נקראו ישראל דלים אלא על עסקי תבואה שנאמר והיה אם זרע ישראל ועלה מדין ועמלק וכתיב וידל ישראל: