Matthew 6:5

5.When thou shalt pray He now gives the same instruction as to prayer, which he had formerly given as to alms. It is a gross and shameful profanation of the name of God, when hypocritcs, in order to obtain glory from men, pray in public, or at least make a pretense of praying. But, as hypocrisy is always ambitious, we need not wonder that it is also blind. Christ, therefore, commands his disciples, if they wish to pray in a right manner, to enter into their closet Some expositors, thinking that this has the appearance of absurdity, give it an allegorical turn, as referring to the inward recesses of the heart: but there is no necessity for such trifling. We are commanded, in many passages, to pray to God or to praise him, in the public assembly, amidst a crowd of men, and before all the people: and that for the purpose, not only of testifying our faith or gratitude, but also of exciting others, by our example, to do the like. Christ does not withdraw us from such an exercise, but only admonishes us to have God always before our eyes when we engage in prayer.

We must not literally interpret the words, enter into thy closet: as if he ordered us to avoid the presence of men, or declared that we do not pray aright, except when there are no witnesses. He speaks comparatively, and means, that we ought rather to seek retirement than desire a crowd of men to see us praying. (428) It is advantageous, indeed, to believers, and contributes to their pouring out, with greater freedom, their prayers and groans before God, to withdraw from the gaze of men. Retirement is also useful for another reason, that our minds may be more free and disengaged from all distracting thoughts: and accordingly Christ himself frequently chose the concealment of some retired spot for the sake of prayer. But this is not the present subject, which is only to correct the desire of vain-glory. To express it in a few words, whether a man prays alone, or in the presence of others, he ought to have the same feelings, as if he were shut up in his closet, and had no other witness but God. When Christ says, thy Father shall reward thee, he declares plainly that all the reward, which is promised to us in any part of Scripture, is not paid as a debt, but is a free gift.