Albert Barnes Commentary Numbers 21:27

"Wherefore they that speak in proverbs say, Come ye to Heshbon; Let the city of Sihon be built and established:" — Numbers 21:27 (ASV)

Those who speak in proverbs - The original word is almost equivalent to “the poets.” The word supplies the title of the Book of Proverbs itself; and is used of the parable proper in (Ezekiel 17:2); of the prophecies of Balaam in (Numbers 23:7–10), (Numbers 24:3–9), etc.; and of a song of triumph over Babylon in (Isaiah 14:4).