1 Peter 1:16

Because it is written (dioti gegraptai). "Because (dioti stronger than oti below) it stands written" (regular formula for O.T. quotation, perfect passive indicative of grapw). The quotation is from Leviticus 11:44 ; Leviticus 19:2 ; Leviticus 20:7 . Reenforced by Jesus in Matthew 5:48 . The future esesqe here is volitive like an imperative.