אֲשֶׁ֨ר הָיָ֤ה דְבַר־יְהוָה֙ אֵלָ֔יו בִּימֵ֛י יֹאשִׁיָּ֥הוּ בֶן־אָמ֖וֹן מֶ֣לֶךְ יְהוּדָ֑ה בִּשְׁלֹשׁ־עֶשְׂרֵ֥ה שָׁנָ֖ה לְמָלְכֽוֹ׃
to whom the word of the LORD came in the days of Josiah the son of Amon, king of Judah, in the thirteenth year of his reign.
Read halakhic rulings (Jewish law) on Jeremiah 1:2: and classical halakhic sources.