וַיְהִ֗י כִּשְׁמֹ֙עַ֙ הַמֶּ֣לֶךְ חִזְקִיָּ֔הוּ וַיִּקְרַ֖ע אֶת־בְּגָדָ֑יו וַיִּתְכַּ֣ס בַּשָּׂ֔ק וַיָּבֹ֖א בֵּ֥ית יְהוָֽה׃
And it came to pass, when king Hezekiah heard it, that he rent his clothes, and covered himself with sackcloth, and went into the house of the LORD.
Read midrashic interpretation of Isaiah 37:1: and classical rabbinic exegesis.