וַיְהִ֗י כַּאֲשֶׁ֨ר כִּלָּ֣ה יִצְחָק֮ לְבָרֵ֣ךְ אֶֽת־יַעֲקֹב֒ וַיְהִ֗י אַ֣ךְ יָצֹ֤א יָצָא֙ יַעֲקֹ֔ב מֵאֵ֥ת פְּנֵ֖י יִצְחָ֣ק אָבִ֑יו וְעֵשָׂ֣ו אָחִ֔יו בָּ֖א מִצֵּידֽוֹ׃
און עס איז געװען, אַז יצחק האָט געענדיקט בענטשן יעקבן, איז װי נאָר יעקב איז אַרױסגעגאַנגען פֿון פֿאַר זײַן פֿאָטער יצחקן, אַזױ איז זײַן ברודער עֵשָׂו אָנגעקומען פֿון זײַן געיעג.
Rashi
יצא יצא [JACOB] WAS YET SCARCE GONE OUT — this means, as one went out the other came in (Midrash Tanchuma, Toldot 11).
Da'at Zekenim
ויהי אך יצא יצא יעקב, “and it happened when Yaakov only just left, etc.”, Yaakov had actually seen Esau come in by the opposite door as it was lit up when opening it, whereas Esau, standing in the light, could not see Yaakov who stood in relative darkness across from him at the other door. (B’reshit Rabbah 66,5)
Rashbam
ויהי אך יצא יצא, this detail has been recorded to illustrate the miracles which were performed in order to enable Yaakov to obtain this blessing. If Esau had returned just one minute sooner, Yaakov would not have secured this blessing.