2 Samuel 20:18

Then she spoke, saying, "They were used to say in old times, 'They shall surely ask counsel at Abel;' and so they settled it.

Deuteronomy 20:10-11

When you draw near to a city to fight against it, then proclaim peace to it.

Treasury of Scripture Knowledge

Summary

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.

They were wont, etc

Bible References

They were wont, etc

Deuteronomy 20:10
When you draw near to a city to fight against it, then proclaim peace to it.