Deuteronomy 2:6
Ye shall buy meat of them for money, that ye may eat; and ye shall also buy water of them for money, that ye may drink. Ye shall buy meat of them for money, that ye may eat; and ye shall also buy water of them for money, that ye may drink.
Israel was to pass through Edom peacefully and without attack, buying food and water with money for their needs. This reflected that they were entering a fertile, well-watered country where supplies could be obtained along the way to Canaan. The command to buy water explains why the miraculous stream stopped before Edom was reached. Its stopping was a sign that the wilderness journey was ending and that the promised passage through Edom was being fulfilled. Israel's doubt and murmuring at that time came from failing to recognize that this provision meant God was fulfilling His promise.