We have here the application made by Israel to the Edomites. The nearest way to Canaan from the place where Israel now lay encamped was through the country of Edom. Now,
I. Moses sends ambassadors to treat with the king of Edom for leave to pass through his country, and gives them instructions what to say, Num 20:14-17. 1. They are to claim kindred with the Edomites: Thus saith thy brother Israel. Both nations descended from Abraham and Isaac, their common ancestors; Esau and Jacob, the two fathers of their respective nations, were twin-brothers; and therefore, for relation-sake, they might reasonably expect this kindness from them; nor needed the Edomites to fear that their brother Israel had any ill design upon them, or would take any advantages against them. 2. They are to give a short account of the history and present state of Israel, which, they take it for granted, the Edomites were no strangers to. And in this there was a double plea: - (1.) Israel had been abused by the Egyptians, and therefore ought to be pitied and succoured by their relations: "The Egyptians vexed us and our fathers, but we may hope our brethren the Edomites will not be so vexatious." (2.) Israel had been wonderfully saved by the Lord, and therefore ought to be countenanced and favoured (Num 20:16): "We cried unto the Lord, and he sent an angel, the angel of his presence, the angel of the covenant, the eternal Word, who had brought us forth out of Egypt, and led us hither." It was therefore the interest of the Edomites to ingratiate themselves with a people that had so great an interest in heaven and were so much its favourites, and it was at their peril if they offered them any injury. It is our wisdom and duty to be kind to those whom God is pleased to own, and to take his people for our people. Come in, thou blessed of the Lord. 3. They are humbly to beg a passport through their country. Though God himself, in the pillar of cloud and fire, was Israel's guide, in following which they might have justified their passing through any man's ground against all the world, yet God would have this respect paid to the Edomites, to show that no man's property ought to be invaded under colour of religion. Dominion is founded in providence, not in grace. Thus when Christ was to pass through a village of the Samaritans, to whom his coming was likely to be offensive, he sent messengers before his face to ask leave, Luk 9:52. Those that would receive kindness must not disdain to request it. 4. They are to give security for the good behaviour of the Israelites in this march, that they would keep in the king's high road, that they would commit no trespass upon any man's property, either in ground or water, that they would not so much as make use of a well without paying for it, and that they would make all convenient speed, as fast as they could well go on their feet, Num 20:17, Num 20:19. Nothing could be offered more fair and neighbourly.
II. The ambassadors returned with a denial, Num 20:18. Edom, that is, the king of Edom, as protector of his country, said, Thou shalt not pass by me; and, when the ambassadors urged it further, he repeated the denial (Num 20:20) and threatened, if they offered to enter his country, it should be at their peril; he raised his trained bands to oppose them. Thus Edom refused to give Israel passage. This was owing, 1. To their jealousy of the Israelites; they feared they should receive promises. And truly, had this numerous army been under any other discipline and command than that of the righteous God himself, who would no more suffer them to do wrong than to take wrong, there might have been cause for this jealousy; but what could they fear from a nation that had statutes and judgments so righteous? 2. It was owing to the old enmity which Esau bore to Israel. If they had no reason to fear damage by them, yet they were not willing to show so much kindness to them. Esau hated Jacob because of the blessing, and now the hatred revived, when the blessing was ready to be inherited. God would hereby discover the ill-nature of the Edomites to their shame, and try the good-nature of the Israelites to their honour: they turned away from him, and did not take this occasion to quarrel with him. Note, We must not think it strange if the most reasonable requests be denied by unreasonable men, and if those be affronted by men whom God favours. I as a deaf man heard not. After this indignity which the Edomites offered to Israel God gave them a particular caution not to abhor an Edomite (Deu 23:7), though the Edomites had shown such an abhorrence of them, to teach us in such cases not to meditate revenge.

And he said, thou shall not go through,.... Which is an absolute and peremptory denial:

and Edom came out against him with much people, and with a strong hand; the king raised the militia of his country, and came at the head of a powerful army to hinder their passing into it; being fearful and jealous, lest such a large body as they were should seize on his country, or spoil it, not relying on their promises; and this might arise also from the old grudge of Esau against Jacob, and which continued in his posterity, and might now be revived upon their going to Canaan to possess the earthly blessing conferred on Jacob and his seed: however, it seems, though the Edomites would not let Israel pass through their country, yet they furnished them with food and drink for their money, Deu 2:28.

if I and my cattle drink of thy water, then I will pay for it--From the scarcity of water in the warm climates of the East, the practice of levying a tax for the use of the wells is universal; and the jealousy of the natives, in guarding the collected treasures of rain, is often so great that water cannot be procured for money.