תּלמוד אויף מיכה 2:13

How do we know that this “passing” means “before”? R. Nahman b. Isaac said: Scripture says, “Then Ahimaaz ran by way of the plain and overran [wa-ya’avor] the Cushite” (II Samuel 18:23). Abaye said: We prove it from here: “And he himself passed over before them” (Genesis 33:3). Or, if you want, I can say: “And their king passed on before them and the Lord at the head of them” (Micah 2:13).

[Where the custom is] to bless, he should bless. Abaye said: This was taught only with regard to after [the Hallel], but before, it is a mitzvah to bless, for Rav Judah said in the name of Rav: For all commandments one blesses before (over) their performance. And from where do we know that the word "over" means before? R. Nahman b. Yitzchak said: As it is written, "Then Ahimaaz ran by the way of the plain and he overran (vayaavor) the Cushite" (II Samuel 18:23). Abaye said from the following: "And he himself passed over (avar) before them" (Genesis 33:3). And if you wish, from the following: "And their king passed on before them (vayaavor), and the Lord at their head" (Micah 2:13).