Luke 19:21

In the Gospel, you have heard both the reward of the good servants and the punishment of the bad. The fault of that servant who was reproved and severely punished was this and only this: that he would not put to use what he had received. He preserved it intact, but his master was looking for a profit from it. God is greedy for our salvation. If such condemnation befalls the servant who did not use what he had received, what should they who lose it expect? We therefore are dispensers. We expend, but you receive. We expect a profit on your part—living good lives—for that is the profit from our dispensing. Do not think that you are free from the obligation of dispensing. Of course, you cannot dispense your gifts as from this higher station of ours, but you can dispense them in whatever station you happen to be. When Christ is attacked, defend him. Give an answer to those who complain. Rebuke blasphemers, but keep yourselves far from any fellowship with them. If in this way you gain anyone, you are putting your gifts to use.

Nothing is said of the other servants, who like wasteful debtors lost all that they had received. By those two servants who gained by trading, are signified that small number, who in two companies were sent as dressers of the vineyard; by the remainder all the Jews. It follows, And they said unto him, Lord, he has ten pounds. And lest this should seem unjust, it is added, For to every one that hath, it shall be given.

(de Quæst. Evan. lib. ii. qu. 46.) Or else; That one of those who well employed their money gained ten pounds, another five, signifies that they acquired them for the flock of God, by whom the law was now understood through grace, either because of the ten commandments of the law, or because he, through whom the law was given, wrote five books; and to this belong the ten and five cities over which He appoints them to preside. For the manifold meanings or interpretations which spring up concerning some individual precept or book, when reduced and brought together in one, make as it were a city of living eternal reasons. Hence a city is not a multitude of living creatures, but of reasonable beings bound together by the fellowship of one law. The servants then who bring an account of that which they had received, and are praised for having gained more, represent those giving in their account who have well employed what they had received, to increase their Lord's riches by those who believe on Him, while they who are unwilling to do this are signified by that servant who kept his pound laid up in a napkin; of whom it follows, And the third came, saying, Lord, behold, here is thy pound, which I have kept laid up in a napkin, &c. For there are some who flatter themselves with this delusion, saying, It is enough for each individual to answer concerning himself, what need then of others to preach and minister, in order that every one should be compelled also to give an account of himself, seeing that in the Lord's sight even they are without excuse to whom the law was not given, and who were not asleep at the time of the preaching of the Gospel, for they might have known the Creator through the creature; and then it follows, For I feared thee, because thou art an austere man, &c. […]

Interest on the Word of God is having in life and deeds things that the Word of God has commanded. When you hear the Word, if you use it and act according to those words that you hear and live according to these words, then you are preparing interest for the Lord. Each of you can make ten talents from five. You will then hear from the Lord, "Well done, good and faithful servant, you shall have power over ten cities." Beware of this, fearing that any one of you may gather "in a napkin" or bury "in the earth" the money that has been received. You know well the nature of the outcome for this kind of man when the Lord comes.

What you have offered to God you shall receive back multiplied. Something like this, although put in another way, is related in the Gospels when in a parable someone received a pound that he might engage in business, and the master of the house demanded the money. If you have caused five to be multiplied to ten, then they are given to you. Hear what Scripture says, "Take his pound, and give it to him who has ten pounds."We therefore appear at least to engage in business for the Lord, but the profits of the business go to us. We appear to offer sacrifice to the Lord, but the things we offer are given back to us. God does not need anything, but he wants us to be rich. He desires our progress through each, individual thing.