Charles Ellicott Commentary 2 Samuel 20:18

"Then she spake, saying, They were wont to speak in old time, saying, They shall surely ask [counsel] at Abel: and so they ended [the matter]." — 2 Samuel 20:18 (ASV)

Ask counsel at Abel. —The simplest and most obvious explanation is here the true one, namely, that Abel had become proverbial for its wisdom. An ancient Jewish interpretation, which has been incorporated into the Targum, is, however, of sufficient interest to be mentioned: “Remember now what is written in the book of the Law—to ask a city about peace first? Have you done so, to ask Abel if they will make peace?” The reference is to Deuteronomy 20:10 and following.