Albert Barnes Commentary Numbers 20:14

"And Moses sent messengers from Kadesh unto the king of Edom, Thus saith thy brother Israel, Thou knowest all the travail that hath befallen us:" — Numbers 20:14 (ASV)

Compare the marginal reference. It appears from comparing Numbers 20:1 with Numbers 33:38, that the assembly must have remained in Kadesh for some three or four months. No doubt time was required for reorganization. In order to gain the banks of the Jordan by the shortest route they had to march nearly due east from Kadesh, and pass through the heart of the Edomite mountains. These are lofty and precipitous, traversed by two or three narrow defiles. Hence, the necessity of the request in Numbers 20:17.

Your brother – An appeal to the Edomites to remember and renew the old kindnesses of Jacob and Esau (Genesis 33:1–17).

It appears from Judges 11:17 that a similar request was addressed to the Moabites.