וּבִשְׁנַ֣ת עֶשְׂרִ֔ים לְיָרָבְעָ֖ם מֶ֣לֶךְ יִשְׂרָאֵ֑ל מָלַ֥ךְ אָסָ֖א מֶ֥לֶךְ יְהוּדָֽה׃
And in the twentieth year of Jeroboam king of Israel began Asa to reign over Judah.
Read kabbalistic (mystical) interpretation of I Kings 15:9: and classical mystical sources.