וְלֹא־יָ֤סַף עוֹד֙ מַלְאַ֣ךְ יְהוָ֔ה לְהֵרָאֹ֖ה אֶל־מָנ֣וֹחַ וְאֶל־אִשְׁתּ֑וֹ אָ֚ז יָדַ֣ע מָנ֔וֹחַ כִּֽי־מַלְאַ֥ךְ יְהוָ֖ה הֽוּא׃
But the angel of the LORD did no more appear to Manoah or to his wife. Then Manoah knew that he was the angel of the LORD.
Read midrashic interpretation of Judges 13:21: and classical rabbinic exegesis.