{For a great and effectual door is opened unto me} (	hura
gar moi ane(9369)gen megal(8820)kai energ(8873)). Second perfect active
indicative of anoig(935c), to open. Intransitive, stands wide open
at last after his years there ( Ac 20:31 ). A wide open door.
What does he mean by energ(8873)? It is a late word in the _Koin(825f).
In the papyri a medical receipt has it for "tolerably strong."
The form energos in the papyri is used of a mill "in working
order," of "tilled land," and of "wrought iron." In the N.T. it
occurs in  Phm 1:6  Heb 4:12  of "the word of God" as "energ(8873)"
(powerful). Paul means that he has at least a great opportunity
for work in Ephesus. {And there are many adversaries} (kai
antikeimenoi polloi). "And many are lying opposed to me," lined
up against me. These Paul mentions as a reason for staying in,
not for leaving, Ephesus. Read  Ac 19  and see the opposition
from Jews and Gentiles with the explosion under the lead of
Demetrius. And yet Paul suddenly leaves. He hints of much of
which we should like to know more ( 1Co 15:32  2Co 1:8f. ).