Exodus 16:18

16:18 When they measured with an omer, the one who gathered much had nothing left over, and the one who gathered little lacked nothing; each one had gathered what he could eat.

Exodus 16:33

16:33 Moses said to Aaron, “Take a jar and put in it an omer full of manna, and place it before the Lord to be kept for generations to come.”

Exodus 16:36

16:36 (Now an omer is one tenth of an ephah.)