Reference for II Samuel 5:4

בֶּן־שְׁלֹשִׁ֥ים שָׁנָ֛ה דָּוִ֖ד בְּמָלְכ֑וֹ אַרְבָּעִ֥ים שָׁנָ֖ה מָלָֽךְ׃

David was thirty years old when he began to reign, and he reigned forty years.

BDB