A.T. Robertson Commentary Acts 10:44

"While Peter yet spake these words, the Holy Spirit fell on all them that heard the word." — Acts 10:44 (ASV)

While Peter yet spake (ετ λαλουντος του Πετρου). Genitive absolute of present participle, still going on.

The Holy Ghost fell (επεπεσεν το πνευμα το αγιον). Second aorist active indicative of επιπιπτω, old verb to fall upon, to recline, to come upon. Used of the Holy Spirit in 8:16; 10:44; 11:15. It appears that Peter was interrupted in his sermon by this remarkable event. The Jews had received the Holy Spirit (2:4), the Samaritans (8:17), and now Gentiles. But on this occasion it was before baptism, as was apparently true in Paul's case (9:17f.). In 8:16; 19:5 the hands of the apostles were also placed after baptism on those who received the Holy Spirit. Here it was unexpected by Peter and by Cornelius and was indubitable proof of the conversion of these Gentiles who had accepted Peter's message and had believed on Jesus Christ as Saviour.