Charles Ellicott Commentary 1 Kings 18:32

"And with the stones he built an altar in the name of Jehovah; and he made a trench about the altar, as great as would contain two measures of seed." — 1 Kings 18:32 (ASV)

Measures. —The “measure,” the third part of the ephah, therefore also often called shalish (a “tierce,” or “third”), was something less than three gallons. A trench to contain only six gallons seems too insignificant for the context; therefore it is supposed that the sense is “large enough for the sowing (as in a furrow) of two measures of seed.”