Acts 4:8

Then Peter, filled with the Holy Spirit, said unto them, Ye rulers of the people, and elders.

Ye rulers of the people ... Peter's respectful language here teaches the same deference and respect of public officials which are binding upon all Christians; but, as Plumptre noted, there was a marked change in Peter:

A few weeks back he had quailed before the soldiers and servants in the palace of the high priest. But now he stands before the Sanhedrin and speaks in the language of respect ... but also that of unflinching boldness.[17]

Regarding the profound and dramatic change discernible in the apostles of Christ which began with the resurrection and was final after Pentecost, Barnes truly declared that "It is not possible to account for this change except on the supposition that this religion is true."[18]

Filled with the Holy Spirit ... Here began to be fulfilled the blessed promise of Jesus to the Twelve that they should not be concerned about what they should say when arraigned before earthly authorities, because the Holy Spirit in that hour would give them the message they were to deliver (Matthew 10:17-19).

[17] E. H. Plumptre, Ellicott's Commentary (Grand Rapids, Michigan: Zondervan Publishing House, 1959), p. 21.

[18] Albert Barnes, op. cit., p. 77.