וַיֹּ֥אמֶר לִ֖י מִי־אָ֑תָּה ויאמר [וָאֹמַ֣ר] אֵלָ֔יו עֲמָלֵקִ֖י אָנֹֽכִי׃
Und er fragte mich: Wer bist du? Ich sprach zu ihm: Ein Amalekiter bin ich.
Rashi
Behold a man came from the camp. The Pesikta1Pesikta Rabosi 12,9. brings an opinion that this man is Doeig,2Doeig HaEdomi is first mentioned in Shmuel 1,21:8. but the explanation is indefensible in my heart.3It is clear from Shmuel 1, 22:18 that Shaul knew Doeig. Therefore, if in fact this man is Doeig, why did Shaul have to ask later in v. 8, “Who are you?” (Seder Hadoros, p. 102).