וַיֹּ֤אמֶר יְהוָה֙ אֵלַ֔י רְאֵ֗ה הַֽחִלֹּ֙תִי֙ תֵּ֣ת לְפָנֶ֔יךָ אֶת־סִיחֹ֖ן וְאֶת־אַרְצ֑וֹ הָחֵ֣ל רָ֔שׁ לָרֶ֖שֶׁת אֶת־אַרְצֽוֹ׃
Tedy rzekł Wiekuisty do mnie: "Patrz! Zaczynam poddawać tobie Sychona, i ziemię jego; pocznijże zdobywać, zdobywać ziemię jego!"
Rashi
החלתי תת לפניך I HAVE BEGUN TO GIVE [SIHON] BEFORE THEE — He cast down the tutelary angel of the Amorites, who was in the upper spheres, beneath Moses’ feet and made him tread upon his neck (cf. Rashi on Numbers 24:2).
Ibn Ezra
I have begun [Hebrew: haḥilloty] The inflectional prefix heh is vocalized with a pattaḥ on account of the subsequent guttural consonant. Compare, “I have raised him up [Hebrew: hairotihu] with justice” [Isaiah 45: 13].
Or HaChaim
ראה החילותי תת לפניך, "Behold, I have begun to deliver up to you, etc." G'd used the word: "I have begun" in the past tense, and the word refers to the time G'd had hardened the spirit of Sichon to deny Israel the right of passage through his country in order to have a pretext to deliver him into Israel's hands. The word החילותי refers to the giving of the land, not to the previous paragraph. Moses misunderstood thinking that the word referred to the whole previous paragraph. This was what caused him to think that G'd had revoked His decree against him and this is what prompted his entreaty at the beginning of the next פרשה as explained there by Sifri.