וַיַּעֲשׂ֧וּ בְנֵי־יִשְׂרָאֵ֛ל הָרַ֖ע בְּעֵינֵ֣י יְהוָ֑ה וַיִּתְּנֵ֧ם יְהוָ֛ה בְּיַד־מִדְיָ֖ן שֶׁ֥בַע שָׁנִֽים׃
And the children of Israel did that which was evil in the sight of the LORD; and the LORD delivered them into the hand of Midian seven years.
Read kabbalistic (mystical) interpretation of Judges 6:1: and classical mystical sources.