By St. John the Prophet
Question 672: If one has debtors who are wealthy, should one demand interest from these people? And if they are poor, should one take back the capital?
Response: It is written of the righteous: "They do not lend their money with interest" (Ps. 15:5). This means that we may receive the capital. Now, if some of them are unable to pay them back, it has also been written about them: "When your friends are in poverty, do not distress them by making demands on them" (Sir. 31:31).
Question 673: What happens if both he and I are poor? Am I committing sin by demanding what I need?
Response: No, you are not committing sin. However, it is good not to distress one's brother, as much as this is possible, if he is too poor to repay us.
Question 726: Someone owes me money, and unless I ignore this a little, we shall never come to have peace. What do you order me to do?
Response: Whoever seeks peace is not deprived of God's peace. "Whoever is faithful in very little is faithful also in much" (Lk. 16:10); and: "Mercy triumphs over judgment" (James 2:13). Therefore, unless a person despises the needs of the world, that person does not attain to the peace of Christ. "The one who began a good work among you will bring it to completion by the day of Jesus Christ" (Phil. 1:6). For this is our prayer: that God may grant us peace, so that we may complete the work of God, as the most holy Guest-Master of the entire Church bore witness.
Question 744: My thought suggests to me that my material resources are tight and that I cannot feed myself or my household, and this causes me sorrow. What does this mean?
Response: This sorrow is human; for, if we had hope in God, he would provide for us as he wants. "Therefore, cast your concern upon the Lord" (1 Pet. 5:7), and he is able to take care of you and your own without sorrow and affliction. Say to him: "Your will be done" (Mt. 6:10 and 26:42), and he will not allow you to grieve or be afflicted. May the Lord have mercy upon you and protect you with his right hand. Amen.
Question 750: If I settle an account and afterward discover that I tricked my brother without wanting to, what should I do?
Response: If the amount is large, then return it to him. If it is small, then examine your thought carefully, asking - from the contrary perspective - what you would do if you were tricked by him and were about to receive the amount; if you find that you would indeed want to receive it, then you too should return it. If you would not receive it, then neither should you give it, unless the person was extremely poor; for in this case, a small amount would make a difference. In this case, you should give him what is fair.
Question 756: If one is buying or selling something, is it a sin to agree on a price, which is higher or lower?
Response: If there is no constraint but the matter is handled in freedom, then it is not a sin to give and take according to the agreed price. However, if one knows that one has gained more, then one should return the amount of one's own accord; for, one will be doing something good and will also be pleasing the other person.
When one agrees on a price with someone that is under one's authority, then one should also examine whether the agreement was made by force; for this is a sin. Rather, one should reassure the other person, by saying: "Brother, I shall not grieve if you do not do as I say; nor shall I offer you more. Therefore, do as you please and as you want."
From The Letters of Saints Barsanuphios and John; translated by John Chryssavgis.