וַיֹּ֤אמֶר אֵלַי֙ לֵאמֹ֔ר הֲל֥וֹא יָדַ֖עְתָּ מָה־אֵ֑לֶּה וָאֹמַ֖ר לֹ֥א אֲדֹנִֽי׃
And he answered me and said: ‘Knowest thou not what these are?’ And I said: ‘No, my lord.’
Read midrashic interpretation of Zechariah 4:13: and classical rabbinic exegesis.