Deuteronomy 3:23

ואתחנן — All forms of the verb חנן signify an ex gratia gift. Although the righteous might make a claim to reward depend Upon their good deeds, yet they solicit from the Omnipresent only an ex gratia gift. [Because He had said to him, (Exodus 33:19) “I will show grace (וחנתי) unto him to whom I will show grace”, he (Moses) when referring to his entreaty of God uses the expression (lit., spoke to Him) "I implored grace (ואתחנן)” (Midrash Tanchuma 5:2:3] — Another explanation is that the idea of an ex gratia gift is not to be stressed; but this is merely one of the ten terms by which prayer is described, as are enumerated in Sifrei Devarim 26:7. בעת ההוא [I IMPLORED GRACE OF GOD] AT THAT TIME — After I had subdued the land of Sihon and Og I thought that perhaps the vow that I should not enter the land was annulled, since this was part of the land of Canaan (cf. Sifrei Devarim 26:8 and Rashi on Numbers 27:12). לאמר TO SAY (i.e. that God should say) — This is one of the three occasions where Moses spoke before the Omnipresent: I will not let You go until You tell me whether You will fulfill my request or not (Sifrei Devarim 26:9; cf. Rashi on Numbers 12:13).

וָאֶתְחַנַּ֖ן אֶל־יְהֹוָ֑ה בָּעֵ֥ת הַהִ֖וא לֵאמֹֽר׃

And I besought the Lord at that time, saying,