Acts 4:31

"The place was shaken," and that made them all the more unshaken. For this is sometimes a token of wrath, sometimes of favor and providence, but on the present occasion, of wrath. For in those times it took place in an unusual manner. Thus, at the Crucifixion, the earth was shaken: and the Lord Himself says, "Then there shall be famines, and pestilences, and earthquakes in divers places." But then the wrath of which it was a sign was against the adversaries: as for the disciples, it filled them with the Spirit. Observe, even the Apostles, after the prayer, are "filled with the Holy Ghost."

These [are the] voices of the Church from which every Church had its origin; these are the voices of the metropolis of the citizens of the new covenant; these are the voices of the apostles; these are voices of the disciples of the Lord, the truly perfect, who, after the assumption of the Lord, were perfected by the Spirit, and called upon the God who made heaven, and earth, and the sea,-who was announced by the prophets,-and Jesus Christ His Son, whom God anointed, and who knew no other [God].

And when they had prayed, the place in which they were gathered was shaken. Those who sought the strength of firm hearts against the deceit of the enemy received the sign of their prayer being heard through the earthquake, so that they might understand that …

And they spoke the word of God with confidence. In the Greek it is added: To everyone willing to believe. Also, in the following reading, when it was said: And the multitude of those who believed were of one heart and one soul, here too …

"And when they had prayed, the place was shaken where they were assembled together." This was a testimony of God's visitation and that they had been heard, because sometimes this is a sign of wrath, and sometimes a sign of visitation. The apostles prayed not …

And when they had prayed,....

The place was shaken - This earthquake was an evidence of the presence of God, and a most direct answer to their prayer, as far as that prayer concerned themselves. The earthquake proclaimed the stretched-out arm of God, and showed them that resistance against his counsels and determinations must come to nought. And they were all filled with the Holy Ghost - And, in consequence of this, they spake the word of God with boldness; a pointed answer to a second part of their request, Act 4:29. A right prayer will always have a right and ready answer. Though these disciples had received the Holy Spirit on the day of pentecost, yet they were capable of larger communications; and what they had then received did not preclude the necessity of frequent supplies, on emergent occasions. Indeed, one communication of this Spirit always makes way and disposes for another. Neither apostle nor private Christian can subsist in the Divine life without frequent influences from on high. Had these disciples depended on their pentecostal grace, they might have sunk now under the terror and menaces of their combined and powerful foes. God gives grace for the time being, but no stock for futurity, because he will keep all his followers continually dependent on himself. With boldness - Παντι τῳ θελοντι πιστευειν, To all who were willing to believe, is added by DE, two others, Augustin, Irenaeus, and Bede.