Sometimes Greek can really be frustrating, especially when it is succinct. Here is a good example. John 3:21 reads, “But the one who does the truth comes to the light, so that his deeds may be clearly seen (φανερωθῇ αὐτοῦ τὰ ἔργα), that (ὅτι) they have been done (ἐστιν εἰργασμένα) in God (ἐν θεῷ).”
Most of the translation is pretty straight forward except for the final phrase. If ἐν is given its normal meaning of sphere, it doesn’t make any sense. If ἐν is instrumental, then you have the awkward idea that the person does the truth, but actually they were done by God.
As always, it is fun to check out the translations.