Matthew 6:4

And then the reward too; consider how great it is. For after He had spoken of the punishment from the one, He points out also the honor derived from the other; from either side urging them, and leading them on to high lessons. Yea, for He is persuading them to know that God is everywhere present, and that not by our present life are our interests limited, but a yet more awful tribunal will receive us when we go hence, and the account of all our doings, and honors, and punishments: and that no one will be hid in doing anything either great or small, though he seem to be hid from men. For all this did He darkly signify, when He said, "Thy Father which seeth in secret shall reward thee openly." Setting for him a great and august assemblage of spectators, and what He desires, that very thing bestowing on him in great abundance. "For what," saith He, "dost thou wish? is it not to have some to be spectators of what is going on? Behold then, thou hast some; not angels, nor archangels, but the God of all." And if thou desire to have men also as spectators, neither of this desire doth He deprive thee at the fitting season, but rather in greater abundance affords it unto thee. For, if thou shouldest now make a display, thou wilt be able to make it to ten only, or twenty, or (we will say) a hundred persons: but if thou take pains to lie hid now, God Himself will then proclaim thee in the presence of the whole universe. Wherefore above all, if thou wilt have men see thy good deeds, hide them now, that then all may look on them with the more honor, God making them manifest, and extolling them, and proclaiming them before all. Again, whereas now they that behold will rather condemn thee as vainglorious; when they see thee crowned, so far from condemning, they will even admire thee, all of them. When therefore by waiting a little, thou mayest both receive a reward, and reap greater admiration; consider what folly it is to cast thyself out of both these; and while thou art seeking thy reward from God, and while God is beholding, to summon men for the display of what is going on. Why, if display must be made of our love, to our Father above all should we make it; and this most especially, when our Father hath the power both to crown and to punish. And let me add, even were there no penalty, it were not meet for him who desires glory, to let go this our theatre, and take in exchange that of men. For who is there so wretched, as that when the king was hastening to come and see his achievements, he would let him go, and make up his assembly of spectators of poor men and beggars? For this cause then, He not only commands to make no display, but even to take pains to be concealed: it not being at all the same, not to strive for publicity, and to strive for concealment.

The intent with which He said all this is shown in that He adds, that your alms may be in secret; that is, in that your good conscience only, which human eye cannot see, nor words discover, though many things are said falsely of many. But your good conscience itself is enough for you towards deserving your reward, if you look for your reward from Him who alone can see your conscience. This is that He adds, And your Father which seeth in secret shall reward you. Many Latin copies have, openly. But in the Greek copies, which are earlier, we have not the word openly.

For it is impossible that God should leave in obscurity any good work of man; but He makes it manifest in this world, and glorifies it in the next world, because it is the glory of God; as likewise the Devil manifests evil, in which is shown the strength of his great wickedness. But God properly makes public every good deed only in that world the goods of which are not common to the righteous and the wicked; therefore to whomsoever God shall there show favour, it will be manifest that it was as reward of his righteousness. But the reward of virtue is not manifested in this world, in which both bad and good are alike in their fortunes.