Numbers 21:23
And Sihon would not suffer Israel to pass through his border: but Sihon gathered all his people together, and went out against Israel into the wilderness: and he came to Jahaz, and fought against Israel. And Sihon would not suffer Israel to pass through his border: but Sihon gathered all his people together, and went out against Israel into the wilderness: and he came to Jahaz, and fought against Israel.
Sihon refused Israel's peaceful request to pass through his territory and border, and instead gathered all his people, the Amorites, and went out against Israel into the wilderness as they traveled toward Canaan. He came to Jahaz and fought them there, and the battle that followed ended in Israel's victory and possession of the Amorite country. That fight at Jahaz belongs to Israel's battles with Sihon and Og, in which a poorly prepared Israel faced powerful, well-equipped and well-armed enemies.
Israel won a complete victory by the Lord's host and took possession of the Amorite country, proving Israel a powerful people. Moses encouraged the people, the Son of God led them in the cloudy pillar, and the ark went with them. Success depended on trusting God and obeying His command to advance, showing that God alone could help them and that His power could carry Israel through danger, while unbelief and rebellion could bring defeat. Israel could have taken the land thirty-eight years earlier if the people had trusted God. This trial was more severe than the earlier command to enter Canaan, which Israel had refused through fear and unbelief, and when Israel had previously gone to battle contrary to God's command, without Moses, the cloudy pillar, or the ark, they were defeated.
After centuries of patience and clear evidence of God's power, the Amorites had rejected the truth, and Sihon's defiant refusal brought them to the point of judgment. God would destroy them as He had judged Pharaoh and his army, and Sihon's defeat showed the destruction that comes to those who defy God. No earthly or demonic power could prevail against Israel while they remained faithful to God.
The verse shows part of Israel's slaying of two kings east of the Jordan just before entering Canaan and of the recent triumph over Sihon, which Balaam knew about. That slaughter, together with the Lord staying the swollen and impetuous Jordan before Israel, filled the kings of the Amorites and the Canaanites and all the surrounding nations with melting fear and great terror. It left Balak king of the Moabites and all Moab exceedingly terrified as Israel moved forward and pitched in the plains of Moab by Jericho. That terror drove Moab to seek help from the elders of Midian and from Balaam against Israel.