I have said, O Jehovah! have mercy upon me. By this verse he shows that in his adversity he did not seek to soothe his mind by flattery, as the greater part of men do, who endeavor to assuage their sorrows by some vain consolation. And, certainly, the man who is guided by the Spirit of God will, when warned of God by the afflictions with which he is visited, frankly acknowledge his sins, and quietly submit to the admonitions of his brethren, nay, he will even anticipate them by a voluntary confession. David here lays down a mark by which he distinguishes himself from the reprobate and wicked, when he tells us that he earnestly entreated that his sin might not be laid to his charge, and that he had sought refuge in the mercy of God. He indeed requests that some alleviation might be granted to him under the affliction which he endured: but he rises to a higher source of relief, when he asks that through the forgiveness of his sins he might obtain reconciliation to God. Those, as we have said elsewhere, invert the natural order of things, who seek a remedy only for the outward miseries under which they labor, but all the while neglect the cause of them; acting as a sick man would do who sought only to quench his thirst, but never thought of the fever under which he labors, and which is the chief cause of his trouble. Before David, therefore, speaks at all of the healing of his soul, that is to say, of his life he first says, Have mercy upon me: and with this we must connect the reason which immediately follows -- for I have sinned against thee. In saying so, he confesses that God is justly displeased with him, and that he can only be restored again to his favor by his sins being blotted out. I take the particle ky, ki, in its proper and natural signification, and not adversatively, as some would understand it. He asks then that God would have mercy upon him because he had sinned. From that proceeds the healing of the soul, which he interposes between his prayer and confession, as being the effect of the compassion and mercy of God; for David expects that as soon as he had obtained forgiveness, he would also obtain relief from his affliction.

I said, Lord - I said in my sickness, or in the trial referred to in the psalm. I called on God to be merciful to me when others had no mercy; to be near to me when others turned away; to save me when pressed down with disease on account of my sins. All that follows relates, like this passage, to what occurred when he was sick; to the thoughts that passed through his mind, and to the treatment which he then experienced from others.
Be merciful unto me - In forgiving my sins, and restoring me to health.
Heal my soul - In restoring my soul to spiritual health by forgiving the sin which is the cause of my sickness; or it may mean, Restore my life - regardng his life as (as it were) diseased and in danger of extinction. The probability, however, is that he had particular reference to the soul as the word is commonly understood, or as designating himself; heal, or restore me.
For I have sinned against thee - Regarding his sin as the cause of his sickness. See the notes at Psalm 38:3-5.

I said, Lord, be merciful unto me - I need thy mercy especially, because I have sinned against thee, and my sin is a deadly wound to my soul; therefore heal my soul, for it has sinned against thee.

I said, Lord, be merciful unto me,.... See Gill on Psalm 40:11;
heal my soul; not that it was diseased with sin in such sense as the souls of other men are; but it is to be understood as a petition for comfort while bearing the sins of others, and which Christ as man stood in need of when in the garden and on the cross; so healing signifies comfort in trouble, as in Isaiah 57:18;
for I have sinned against thee; or "unto thee", or "before thee", as the Targum; not that any sin was committed by him in his own person, but he having all the sins of his people on him, which he calls his own, Psalm 40:12; he was treated as a sinner, and as guilty before God, Isaiah 53:12; and so the words may be read, "for I am a sinner unto thee" (u); I am counted as one by thee, having the sins of my people imputed to me; and am bound unto thee, or under obligation to bear the punishment of sin; or thus, "for I have made an offering for sin unto thee" (w), so the word is used, Leviticus 6:26; and so it might be rendered in Leviticus 5:7; and perhaps may be better rendered so in Leviticus 4:3; and be understood, not of the sin of the anointed priest, but of his offering a sacrifice for the soul that sinned through ignorance, Psalm 41:2, which offering is directed to: and then the sense here is, heal me, acquit me, discharge me, and deliver me out of this poor and low estate in which I am; for I have made my soul an offering for sin, and thereby have made atonement for all the sins of my people laid upon me; and accordingly he was acquitted and justified, 1-Timothy 3:16.
(u) "tibi", Pagninus, Montanus, Cocceius. (w) "Obtuli sacrificium pro peccato", Gussetius, Ebr. Comment. p. 249, 923.

I said--I asked the mercy I show.
heal my soul--(Compare Psalm 30:2). "Sin and suffering are united," is one of the great teachings of the Psalm.

(Hebrews.: 41:5-7) He, the poet, is treated in his distress of soul in a manner totally different from the way just described which is so rich in promises of blessing. He is himself just such a דּל, towards whom one ought to manifest sympathising consideration and interest. But, whilst he is addressing God in the language of penitential prayer for mercy and help, his enemies speak evil to him, i.e., with respect to him, wishing that he might die and that his name might perish. רפאה .hs is as an exception Milra, inasmuch as א draws the tone to its own syllable; cf. on the other hand רגזה, Isaiah 32:11 (Hitzig). מתי (prop. extension, length of time) has only become a Semitic interrogative in the signification quando by the omission of the interrogative אי (common Arabic in its full form Arab. 'ymtâ, êmata). ואבד is a continuation of the future. In Psalm 41:7 one is singled out and made prominent, and his hypocritically malicious conduct described. ראות of a visit to a sick person as in 2-Samuel 13:5., 2-Kings 8:29. אם is used both with the perf. (Psalm 50:18; Psalm 63:7; Psalm 78:34; Psalm 94:18; Genesis 38:9; Amos 7:2; Isaiah 24:13; Isaiah 28:25) and with the fut. (Psalm 68:14; Job 14:14), like quum, as a blending together of si and quando, Germ. wenn (if) and wann (when). In ידבר לבו two Rebias come together, the first of which has the greater value as a distinctive, according to the rule laid down in Baer's Psalterium, p. xiv. Consequently, following the accents, it must not be rendered: "falsehood doth his heart speak." The lxx, Vulgate, and Targum have discerned the correct combination of the words. Besides, the accentuation, as is seen from the Targum and expositors, proceeds on the assumption that לבּו is equivalent to בּלבּו. But why may it not be the subject-notion: "His heart gathereth" is an expression of the activity of his mind and feelings, concealed beneath a feigned and friendly outward bearing. The asyndeton portrays the despatch with which he seeks to make the material for slander, which has been gathered together, public both in the city and in the country.

Heal - The soul is said to be healed, when it is pardoned and purged. For - For I acknowledge that I have sinned.