וַיָּבֹ֥א אֶל־אָבִ֖יו וַיֹּ֣אמֶר אָבִ֑י וַיֹּ֣אמֶר הִנֶּ֔נִּי מִ֥י אַתָּ֖ה בְּנִֽי׃
야곱이 아버지에게 나아가서 내 아버지여 하고 부른대 가로되 내가 여기 있노라 내 아들아 네가 누구냐
Radak on Genesis
ויבא אל אביו, into the room where he was lying down. He called to him: אבי, seeing he (Yitzchok) could not see him.
Radak on Genesis
?מי אתה, seeing that he had addressed him simply with the word אבי, he had doubts about whose voice he had heard he had to ask: “who are you?”