Albert Barnes 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)

The Holy Ghost fell, etc. Endowing them with the power of speaking with other tongues (Acts 10:46). Of this the apostle Peter makes much in his argument in Acts 11:17. By this God showed that the Gentiles were to be admitted to the same privileges with the Jews, and to the blessings of salvation in the same manner. (Compare to Acts 2:1-4.)

Which heard the word. The word of God; the message of the gospel.