תּלמוד אויף ישעיהו 66:10

and the sages say, 'Anyone who does work on the Ninth of Av and does not mourn over Jerusalem will not see its rejoicing, as it is stated (Isaiah 66:10), "Rejoice with Jerusalem and be glad with her, all who love her; be gleeful with glee, all who mourn over her."' From here, they said, 'Anyone who mourns over Jerusalem will merit to see her rejoicing; and who does not mourn over Jerusalem will not see her rejoicing.'" It was similarly taught thusly, "Anyone who eats meat and drinks wine on the Ninth of Av, about him the verse states (Ezekiel 32:27), 'and whose iniquities were upon their bones.'"