Build each other up (oikodomeite heis ton hena). Literally, build ye, one the one (heis nominative in partitive apposition with unexpressed humeis subject of oikodomeite. Then ton hena the accusative in partitive apposition with the unexpressed heautous or allè„lous. See the same idiom in 1Co 4:6 one in behalf of the one, heis huper tou henos. Build is a favourite Pauline metaphor.