Luke 16:13

Not because the Lord is two, but one. For although there are who serve mammon, yet he knoweth no rights of lordship; but has himself placed upon himself a yoke of servitude. There is one Lord, because there is one God. Hence it is evident, that the power of the Father and the Son is one: and He assigns a reason, thus saying, For either he will hate the one, and love the other; or else he will hold to the one, and despise the other.

(de Qu. Ev. lib. ii. q. 36.) But these things were not spoken indifferently or at random. For no one when asked whether he loves the devil, answers that he loves him, but rather that he hates him; but all generally proclaim that they love God. Therefore either he will hate the one, (that is, the devil,) and love the other, (that is, God;) or will hold to the one, (that is, the devil, when he pursues as it were temporal wants,) and will despise the other, (that is, God,) as when men frequently neglect His threats for their desires, who because of His goodness flatter themselves that they will have impunity.

(ex Hier.) Let then the covetous hear this, that we can not at the same time serve Christ and riches; and yet He said not, "Who has riches," but, who serves riches; for ho who is the servant of riches, watches them as a servant; but he who has shaken off the yoke of servitude, dispenses them as a master; but he who serves mammon, verily serves him who is set over those earthly things as the reward of his iniquity, and is called the prince of this world. (John 12:31, 2 Cor. 4:4.)

Thus then hitherto He has taught us how faithfully we ought to dispose of our wealth. But because the management of our wealth according to God is no otherwise obtained than by the indifference of a mind unaffected towards riches, He adds, No man can serve two masters.

Thus then Christ taught those who abound in riches, earnestly to love the friendship of the poor, and to have treasure in heaven. But He knew the sloth of the human mind, how that they who court riches bestow no work of charity upon the needy. That to such men there results no profit of spiritual gifts, He shows by obvious examples, adding, He that is faithful in that which is least is faithful also in much; and he that is unjust in the least is unjust also in much. Now our Lord opens to us the eye of the heart, explaining what He had said, adding, If therefore ye have not been faithful in the unrighteous mammon, who will commit to your trust the true riches? That which is least then is the mammon of unrighteousness, that is, earthly riches, which seem nothing to those that are heavenly wise. I think then that a man is faithful in a little, when he imparts aid to those who are bowed down with sorrow. If then we have been unfaithful in a little thing, how shall we obtain from hence the true riches, that is, the fruitful gift of Divine grace, impressing the image of God on the human soul? But that our Lord's words incline to this meaning is plain from the following; for He says, And if ye have not been faithful in that which is another man's, who shall give you that which is your own? But the conclusion of the whole discourse is what follows, Ye cannot serve God and mammon. Let us then transfer all our devotions to the one, forsaking riches.