וַיְהִ֗י בִּשְׁכֹּ֤ן יִשְׂרָאֵל֙ בָּאָ֣רֶץ הַהִ֔וא וַיֵּ֣לֶךְ רְאוּבֵ֔ן וַיִּשְׁכַּ֕ב֙ אֶת־בִּלְהָ֖ה֙ פִּילֶ֣גֶשׁ אָבִ֑֔יו וַיִּשְׁמַ֖ע יִשְׂרָאֵֽ֑ל (פ) וַיִּֽהְי֥וּ בְנֵֽי־יַעֲקֹ֖ב שְׁנֵ֥ים עָשָֽׂר׃
And it came to pass, while Israel dwelt in that land, that Reuben went and lay with Bilhah his father’s concubine; and Israel heard of it. Now the sons of Jacob were twelve:
Read kabbalistic (mystical) interpretation of Genesis 35:22: and classical mystical sources.