John Gill Commentary Acts 11:15

"And as I began to speak, the Holy Spirit fell on them, even as on us at the beginning." — Acts 11:15 (ASV)

And as I began to speak
, That is, whilst he was speaking; the word "begin" with Luke, both, in his Gospel and in this history, is used not to denote the time or order of any action, but the thing itself; as in (Luke 4:21) (20:9) (Acts 1:1) for otherwise it was towards the close, and not at the beginning of his discourse, that what follows happened:

the Holy Ghost fell on them, as on us at the beginning ;
of our ministry, since the death, resurrection, and ascension of Christ; meaning on the day of Pentecost, and that the Holy Ghost fell on Cornelius and those that were with him, in a like visible form, and in the same kind of gifts, as speaking with tongues, as on them.