Reference for II Kings 21:1

בֶּן־שְׁתֵּ֨ים עֶשְׂרֵ֤ה שָׁנָה֙ מְנַשֶּׁ֣ה בְמָלְכ֔וֹ וַחֲמִשִּׁ֤ים וְחָמֵשׁ֙ שָׁנָ֔ה מָלַ֖ךְ בִּירוּשָׁלִָ֑ם וְשֵׁ֥ם אִמּ֖וֹ חֶפְצִי־בָֽהּ׃

Manasseh was twelve years old when he began to reign; and he reigned five and fifty years in Jerusalem; and his mother’s name was Hephzi-bah.

BDB