They spoke what they seriously intended and would have done, if he had given them quiet passage; but withal they knew that Sihon would not do it, and that he would withstand them, and that they should subdue him and take his land, as God had told them before they sent this message, as appears from Deuteronomy 2:21,26,27; and accordingly God hardened his spirit, and made his heart obstinate, for this end, that he might deliver him into Israel's hand there, Numbers 21:31. And no wonder, for he and his people were Amorites, and therefore devoted to destruction, as all that people were.
Related Commentaries of Numbers 21:22
Numbers 21:22
22 Let me pass through thy land: we will not turn into the fields, or into the vineyards; we will not drink of the waters of the well: but we will go along by the king's high way, until we be past thy borders.