וְהֵ֙מָּה֙ אָמְר֣וּ אֶֽל־יִרְמְיָ֔הוּ יְהִ֤י יְהוָה֙ בָּ֔נוּ לְעֵ֖ד אֱמֶ֣ת וְנֶאֱמָ֑ן אִם־לֹ֡א כְּֽכָל־הַ֠דָּבָר אֲשֶׁ֨ר יִֽשְׁלָחֲךָ֜ יְהוָ֧ה אֱלֹהֶ֛יךָ אֵלֵ֖ינוּ כֵּ֥ן נַעֲשֶֽׂה׃
Then they said to Jeremiah: ‘The LORD be a true and faithful witness against us, if we do not even according to all the word wherewith the LORD thy God shall send thee to us.
Read midrashic interpretation of Jeremiah 42:5: and classical rabbinic exegesis.