15 Therefore, he says, “For I have not known tradings.” What are these tradings? Let traders hear and change their life; and if they have been such, be not such; let them not know what they have been, let them forget; lastly, let them not approve, not praise; let them disapprove, condemn, be changed, if trading is a sin. For on this account, O thou trader, because of a certain eagerness for getting, whenever you shall have suffered loss, you will blaspheme; and there will not be in you that which has been spoken of, “all the day long Your praise.”
But whenever for the price of the goods which you are selling, thou not only liest, but even falsely swearest; how in your mouth all the day long is there the praise of God? While, if you are a Christian, even out of your mouth the name of God is being blasphemed, so that men say, see what sort of men are Christians! Therefore if this man for this reason speaks the praise of God all the day long, because he has not known tradings; let Christians amend themselves, let them not trade.
But a trader says to me, behold I bring indeed from a distant quarter merchandise unto these places, wherein there are not those things which I have brought, by which means I may gain a living: I ask but as reward for my labour, that I may sell dearer than I have bought: for whence can I live, when it has been written, “the worker is worthy of his reward”? But he is treating of lying, of false swearing. This is the fault of me, not of trading: for I should not, if I would, be unable to do without this fault.
I then, the merchant, do not shift my own fault to trading: but if I lie, it is I that lie, not the trade. For I might say, for so much I bought, but for so much I will sell; if you please, buy. For the buyer hearing this truth would not be offended, and not a whit less all men would resort to me: because they would love truth more than gain. Of this then, he says, admonish me, that I lie not, that I forswear not; not to relinquish business whereby I maintain myself. For to what do you put me when you put me away from this?
Perchance to some craft? I will be a shoemaker, I will make shoes for men. Are not they too liars? Are not they too false-swearers? Do they not, when they have contracted to make shoes for one man, when they have received money from another man, give up that which they were making, and undertake to make for another, and deceive him for whom they have promised to make speedily? Do they not often say, today I am about it, today I'll get them done? Secondly, in the very sewing do they not commit as many frauds?
These are their doings and these are their sayings: but they are themselves evil, not the calling which they profess. All evil artificers, then, not fearing God, either for gain, or for fear of loss or want, do lie, do forswear themselves; there is no continual praise of God in them. How then do you withdraw me from trading? Would you that I be a farmer, and murmur against God thundering, so that, fearing hail, I consult a wizard, in order to learn what to do to protect me against the weather; so that I desire famine for the poor, in order that I may be able to sell what I have kept in store?
Unto this do you bring me? But good farmers, you say, do not such things. Nor do good traders do those things. But why, even to have sons is an evil thing, for when their head is in pain, evil and unbelieving mothers seek for impious charms and incantations? These are the sins of men, not of things. A trader might thus speak to me— Look then, O Bishop, how thou understand the tradings which you have read in the Psalm: lest perchance thou understand not, and yet forbid me trading. Admonish me then how I should live; if well, it shall be well with me: one thing however I know, that if I shall have been evil, it is not trading that makes me so, but my iniquity. Whenever truth is spoken, there is nothing to be said against it.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)