Adam Clarke on John 7:21

I have done one work - That of curing the impotent man, already referred to. See Joh 5:9.

And ye all marvel - or, ye all marvel because of this. Some have δια τουτο, in connection with θαυμαζετε, which the common pointing makes the beginning of the next verse, and which, in our common version, is translated therefore; but this word conveys no meaning at all, in the connection in which it is thus placed. Proof of this construction Kypke gives from Themistius, Strabo, and Aelian. All the eminent critics are on the side of this arrangement of the words.