A.T. Robertson Commentary 1 John 3:13

"Marvel not, brethren, if the world hateth you." — 1 John 3:13 (ASV)

If (ε). Common construction after θαυμαζω (wonder) rather than οτ (that, because). Present imperative here with μη means "cease wondering." Note μη θαυμασηις (do not begin to wonder) in Joh 3:6 (an individual case). See this same condition and language in Joh 15:18.