וַיֹּ֥אמֶר יְשַׁעְיָ֖הוּ אֶל־חִזְקִיָּ֑הוּ שְׁמַ֖ע דְּבַר־יְהוָ֥ה צְבָאֽוֹת׃
Then said Isaiah to Hezekiah: ‘Hear the word of the LORD of hosts:
Read halakhic rulings (Jewish law) on Isaiah 39:5 from the Mishneh Torah and classical halakhic sources, free online.