John Gill Commentary Acts 15:7

"And when there had been much questioning, Peter rose up, and said unto them, Brethren, ye know that a good while ago God made choice among you, that by my mouth the Gentiles should hear the word of the gospel, and believe." — Acts 15:7 (ASV)

And when there had been much disputing
Pro and con upon this subject; many had spoken; and much had been said, and a great deal of time had been taken up about the thing in controversy:

Peter rose up;
not only out of respect to this venerable assembly, but to signify that he had something to say; and he stood up that he might be the better heard. Beza's ancient copy reads, "rose up in spirit";

and said unto them, men and brethren:
an usual form of address with the Jews; (Acts 7:2)

you know how that a good while ago;
or "from ancient days"; or "from the beginning", as the Ethiopic version renders it; from the beginning of the preaching of the Gospel, after the ascension of Christ; quickly after the effusion of the Spirit on the day of Pentecost: it is thought, by some, to be ten or eleven, and, by others, to be twenty years ago, or thereabout:

God made choice among us;
the apostles; the Alexandrian copy reads, "among you"; the sense is the same, for Peter must be supposed as directing his discourse chiefly to the apostles:

that the Gentiles by my mouth should hear the word of the Gospel,
and believe; referring to the case of Cornelius, and his family: and his sense is, that some years ago it pleased God, in his providence, to single him out from the rest of the apostles, and in a very extraordinary manner to call him to go to Caesarea, and preach the gospel to Cornelius, and those that were in his house, that hearing they might believe in Christ.