הֵ֣ן הֵ֜נָּה הָי֨וּ לִבְנֵ֤י יִשְׂרָאֵל֙ בִּדְבַ֣ר בִּלְעָ֔ם לִמְסָר־מַ֥עַל בַּיהוָ֖ה עַל־דְּבַר־פְּע֑וֹר וַתְּהִ֥י הַמַּגֵּפָ֖ה בַּעֲדַ֥ת יְהוָֽה׃
Behold, these caused the children of Israel, through the counsel of Balaam, to revolt so as to break faith with the LORD in the matter of Peor, and so the plague was among the congregation of the LORD.
Read kabbalistic (mystical) interpretation of Numbers 31:16: and classical mystical sources.