Deuteronomy 2:26

And I sent messengers from Nehardea, which is by the wilderness of Kedemoth, to Sihon king of the Amorites, with words of peace, saying,

from the wilderness of Qedemot In my opinion this is the same wilderness as the one called “Mattanah” [Numbers 21: 18].

ממדבר קדמות, “from the wilderness of K’demot.” This means that the region in question had been a barren desert before G–d had decided to produce water from the rock Moses had struck. Seeing that most of the territory ruled over by Sichon during Moses’ time used to belong previously to either Moav or Ammon, both nations whose territory was out of bounds for the Israelites, they offered to traverse it peacefully. The territory ruled over by Og, which previously was occupied by the Refaim, was not the subject of such an offer by the Israelites. No peace offering under any conditions other than the population relocating themselves was extended to any of the seven Canaanite tribes. They were also not eligible for conversion to Judaism. A different interpretation of the words: ממדבר קדמות. G–d had explained to Moses that legally speaking, instead of sending Moses and Aaron to warn Pharaoh to release His people, He was entitled on the basis of their record to kill the Egyptians without any warning at all. Nonetheless, He went out of His way to offer them a chance to rehabilitate themselves. (Exodus 8,15) The same was true at Mount Sinai, prior to G–d revealing Himself to the Israelites and giving them His Torah. He knew full well that the Ishmaelites or Edomites when offered the Torah would reject it out of hand; nevertheless, He went through the motions of offering it to them. (Compare Deuteronomy 33,2) Here too, Moses emulated what he had learned from G–d and dispatched messengers to ask for permission to traverse the land of Sichon, offering economic benefits to him such as offering to pay for water, although the Israelites had their own supply of water. According to our sages, Moses actually sent two letters to him. In one letter he offered peaceful relations. In the second letter he warned him that if that offer were to be turned down the Israelites would declare war upon him and his nation. According to Rabbi Shimon ben Lakish, Moses did not waste two letters on Sichon, but in the first section of his letter he offered peaceful relations, whereas in the second half he spelled out that the alternative would be war. He based himself on Psalms 120,7: אני שלום וכי אדבר המה למלחמה, “when I offer peace, they are nonetheless bent on war.” Considering this, G–d told the Israelites that because these people were bent upon war against you I will let you inherit their land in peace, as we know from Psalms 37,11: וענוים יירשו ארץ והתענגו על רוב שלום, “but the lowly shall inherit the land and delight in abundant well-being”.