But Peter rehearsed - Greek: Peter beginning, explained it to them in order; that is, he began with the vision which he saw, and gave a narrative of the various events in order, as they actually occurred. A simple and unvarnished statement of facts is usually the best way of disarming prejudice and silencing opposition. Opposition most commonly arises from prejudice, or from false and exaggerated statements, and such opposition can be best removed, not by angry contention, but by an unvarnished relation of facts. In most cases prejudice will thus be disarmed, and opposition will die away, as was the case in regard to the admission of the Gentiles to the church.
And expounded it - Explained it; stated it as it actually occurred.
In order - One event after another, as they happened. He thus showed that his own mind had been as much biased as theirs, and stated in what manner his prejudices had been removed. It often happens that those who become most zealous and devoted in any new measures for the advancement of religion were as much opposed to them at first as others. They are led from one circumstance to another, until their prejudices die away, and the providence and Spirit of God indicate clearly their duty.

But Peter rehearsed the matter from the beginning, and expounded it by order - Εξετιθετο αυτοις καθεξης. This is the very style of St. Luke; see his Gospel, Luke 1:3. To remove their prejudice, and to give them the fullest reasons for his conduct, he thought it best to give them a simple relation of the whole affair; which he does, as we have seen in the preceding chapter, with a few additional circumstances here. See the notes before.

But Peter rehearsed the matter from the beginning,.... Of the vision at Joppa;
and expounded it by order unto them; or related every particular, in a very methodical and orderly manner: he did not insist upon his authority as an apostle, and much less pretended to a primacy to the rest of the apostles; but submitted to have his case heard, examined, and judged of by the body of the brethren.

But Peter rehearsed the matter from the beginning. Thus showing that he acted under the Divine orders. See notes in preceding chapter.
These six brethren accompanied me. These were brethren of Joppa, but Peter had taken them to Jerusalem to confirm his words. He knew his course would be called into question.
Whereby thou and all thy house shall be saved. Note the import of these words of the angel to Cornelius: (1) Notwithstanding his prayers, alms, devotion, and justice, he was not yet saved. Only the gospel could save him. God's mercy was shown in bringing him the gospel. (2) This is the first instance named in Acts of a household baptism. Were there any infants? Who are meant is seen by reference to Acts 10:24, "his kinsmen and near friends." These "heard" (Acts 10:44), were baptized with the Holy Spirit, and baptized in water (Acts 10:47-48).
As on us at the beginning. Note that Peter compares the outpouring on the Gentiles with that of the day of Pentecost. He calls both instances "baptisms of the Holy Spirit." Miraculous signs accompanied each instance. Have we a right to speak of a baptism of the Holy Spirit without such signs? The gift of the Holy Spirit with its fruit (Galatians 5:22-23) is promised to every obedient believer, but the baptism of the Holy Spirit seems to have been extraordinary and special. Note also that Peter calls the Day of Pentecost the Beginning. The Beginning of what? Of the preaching of the New Covenant, of the Great Commission, of the conditions of the gospel under the reign of the exalted King and Savior, of the church of Christ on earth.
What was I, that I could withstand God? All these extraordinary signs were then given in order to show Peter and the Jewish Christians that the Gentiles were also accepted.

Peter laid all things before them - So he did not take it ill to be questioned, nor desire to be treated as infallible. And he answers the more mildly because it related to a point which he had not readily believed himself.