While he himself went a day's journey into the desert- I Ki.19:4

This is a very ancient method of estimating distances that is still used in some parts of the Middle East.

A "day's journey" varies, according to circumstances and difficulty of traveling. It ranged from 18 to 30 miles (about 36-50 km)

The ordinary day's journey of the Scriptures is probably closer to 20 miles (34 km) See also Gen.30:36 and 31:23; Ex.5:3 and 8:27; Num.11:31; Deut.1:2; Ki.3:9; and Luke 2:44.

The Sabbath day's walk (journey) was a shorter distance- only about 1/2 mile (1 km) or 2000 cubits