Of Prayer, by John Calvin, tr. Henry Beveridge , at sacred-texts.com
As God in his word enjoins common prayer, so public temples are the places destined for the performance of them, and hence those who refuse to join with the people of God in this observance have no ground for the pretext, that they enter their chamber in order that they may obey the command of the Lord. For he who promises to grant whatsoever two or three assembled in his name shall ask (Matthew 18:20), declares, that he by no means despises the prayers which are publicly offered up, provided there be no ostentation, or catching at human applause, and provided there be a true and sincere affection in the secret recesses of the heart. 16 If this is the legitimate use of churches (and it certainly is), we must, on the other hand, beware of imitating the practice which commenced some centuries ago, of imagining that churches are the proper dwellings of God, where he is more ready to listen to us, or of attaching to them some kind of secret sanctity, which makes prayer there more holy. For seeing we are the true temples of God, we must pray in ourselves if we would invoke God in his holy temple. Let us leave such gross ideas to the Jews or the heathen, knowing that we have a command to pray without distinction of place, "in spirit and in truth" (John 4:23). It is true that by the order of God the temple was anciently dedicated for the offering of prayers and sacrifices, but this was at a time when the truth (which being now fully manifested, we are not permitted to confine to any material temple) lay hid under the figure of shadows. Even the temple was not represented to the Jews as confining the presence of God within its walls, but was meant to train them to contemplate the image of the true temple. Accordingly, a severe rebuke is administered both by Isaiah and Stephen, to those who thought that God could in any way dwell in temples made with hands (Isaiah 66:2; Acts 7:48).
16 See Book I. chap. xi. sec. 7,13, on the subject of images in churches. Also Book IV. chap. iv. sec. 8, and chap. v. sec. 18, as to the ornaments of churches.