Philo Judaeus De Cherubim 122

[122] Therefore, if you consider the matter, you will find that all men, and especially those who have been alluded to as giving gratuitously, sell rather than give; and that they, who we fancy are receiving favours, are, in reality, purchasing the benefits which they derive; for they who give, hoping to receive a requital, such as praise or honour, and seeking for a return of the favour which they are conferring, under the specious name of a gift, are, in reality, making a bargain. Since it is usual, for those who sell, to receive a price in return for what they part with; but they who, receiving presents, feel anxiety to make a return for them, and make such a return in due season, they in reality perform the part of purchasers; for as they know how to receive, so also do they know how to requite.