בִּשְׁנַ֛ת שְׁמוֹנֶ֥ה עֶשְׂרֵ֖ה לַמֶּ֣לֶךְ יָרָבְעָ֑ם וַיִּמְלֹ֥ךְ אֲבִיָּ֖ה עַל־יְהוּדָֽה׃
In the eighteenth year of king Jeroboam began Abijah to reign over Judah.
Read midrashic interpretation of II Chronicles 13:1: and classical rabbinic exegesis.