Psalms 36:10

They were formed by you so as to be able, if they wished, both to know you and to hope in you, and to enjoy the good things stemming from this.

(Verses 9, 10.) Therefore, He fittingly substitutes: 'For with you is the fountain of life: and in your light we shall see light.' Extend your mercy to those who know you, and your righteousness to those who are upright in heart. Indeed, after the remembrance of heavenly benefits, gratitude is rightly ascribed to our Lord Jesus Christ, who, as the life-giving fountain of eternity, descended to earth to water the dryness of our hearts. The same is the brightness of the glory of God the Father, and the image of his substance; and therefore in his true light, which enlightens every man that comes into this world, we shall see, he says, the Father; because God is light. It is also rightly said: In your light we shall see light; according to that: He who sees me, sees also my Father (John 14:9). Therefore, with you, O Source of life, we shall see the Father present. For just as you, being the Word of God, were with the Father in the beginning: so the Father is always with you, who are in him. For indeed in Him is present that which is. But the coming of the Lord and Savior was prophesied, who, when He was about to come into the world, said: 'I and the Father are one' (John 10:30); that is, we are one light, just as we are one name. Through the unity of light and name, we are both one; indeed, the Trinity is one in the unity of substance, but with the distinction of each person. The Trinity signifies the distinction of persons, the unity signifies the power. It can also be said of the Father: 'For with you is the fountain of life,' that is, in you from whom life proceeded, there was the Word, and He always was, because He was with you. All things were made through him, and in him was life, and he has shown himself to us, so that the hearts of men may be illuminated with the knowledge of your majesty. Therefore, extend your mercy to those who know you. […]

"Show forth Thy Mercy unto them that know Thee; Thy Righteousness to them that are of a right heart" (ver. 10). As I have said, Those are of a right heart who follow in this life the Will of God. The will of God is sometimes that thou shouldest be whole, sometimes that thou shouldest be sick. If when thou art whole God's Will be sweet, and when thou art sick God's Will be bitter; thou art not of a right heart. Wherefore? Because thou wilt not make right thy will according to God's Will, but wilt bend God's Will to thine. That is right, but thou art crooked: thy will must be made right to That, not That made crooked to thee; and thou wilt have a right heart. It is well with thee in this world; be God blessed, who comforteth thee: it goeth hardly with thee in this world; be God blessed, because He chasteneth and proveth thee; and so wilt thou be of a right heart, saying, "I will bless the Lord at all times: His Praise shall be ever in my mouth."

He does not, indeed, extend His mercy to them because they know Him, but that they may know Him; nor is it because they are upright in heart, but that they may become so, that He extends to them His righteousness, whereby He justifies the ungodly. This meditation does not elevate with pride: this sin arises when any man has too much confidence in himself, and makes himself the chief end of living. Impelled by this vain feeling, he departs from that fountain of life, from the draughts of which alone is imbibed the holiness which is itself the good life, and from that unchanging light, by sharing in which the reasonable soul is in a certain sense inflamed, and becomes itself a created and reflected luminary...

"Extend your mercy." Here he turns to prayer, and asks for the mercy of God. And first he asks his petition regarding others. Second, regarding himself, at "Let not the foot of pride come to me." He asks two things, corresponding to two kinds of …