וְכִרְא֨וֹת שָׁא֜וּל אֶת־דָּוִ֗ד יֹצֵא֙ לִקְרַ֣את הַפְּלִשְׁתִּ֔י אָמַ֗ר אֶל־אַבְנֵר֙ שַׂ֣ר הַצָּבָ֔א בֶּן־מִי־זֶ֥ה הַנַּ֖עַר אַבְנֵ֑ר וַיֹּ֣אמֶר אַבְנֵ֔ר חֵֽי־נַפְשְׁךָ֥ הַמֶּ֖לֶךְ אִם־יָדָֽעְתִּי׃
And when Saul saw David go forth against the Philistine, he said unto Abner, the captain of the host: ‘Abner, whose son is this youth?’ And Abner said: ‘As thy soul liveth, O king, I cannot tell.’
Read kabbalistic (mystical) interpretation of I Samuel 17:55: and classical mystical sources.