וְהָיָה֙ בַּיּ֣וֹם הַה֔וּא יִדַּ֖ל כְּב֣וֹד יַעֲקֹ֑ב וּמִשְׁמַ֥ן בְּשָׂר֖וֹ יֵרָזֶֽה׃
And it shall come to pass in that day, That the glory of Jacob shall be made thin, And the fatness of his flesh shall wax lean.
Read halakhic rulings (Jewish law) on Isaiah 17:4: and classical halakhic sources.