'One third' in the Bible

Also you shall provide a grain offering with it morning by morning, one-sixth of an ephah with one-third of a hin of oil to sprinkle on the finely-milled flour. This is a perpetual ordinance for a continual grain offering to the Lord.

“It will come about in all the land,”Declares the Lord,“Two parts in it will be cut off and perish,But the third will be left alive.