A.T. Robertson Commentary John 3:27

"John answered and said, A man can receive nothing, except it have been given him from heaven." — John 3:27 (ASV)

Except it have been given him from heaven (εαν μη η δεδομενον αυτω εκ του ουρανου). See the same idiom in Joh 6:65 (cf. 19:11). Condition of third class, undetermined with prospect of determination, εαν μη with the periphrastic perfect passive subjunctive of διδωμ. The perfect tense is rare in the subjunctive and an exact rendering into English is awkward, "unless it be granted him from heaven." See 1 Corinthians 4:7 where Paul says the same thing.