Abbott-Smith Manual Greek Lexicon
εἰκῇ (G1500)
6 εἰκῇ ( -ῆ , Rec., as in cl.), adv. , [in LXX: Pr 28:25 ( εἰκῇ )* ;] without cause or reason : Mt 5:22 (E, mg.), Col 2:18 ( ICC ). vainly, fruitlessly, to no purpose : Ro 13:4 , I Co 15:2 , Ga 3:4 4:11 , Col 2:18 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain