Psalm 40:
For innumerable evils have compassed me about:
mine iniquities have taken hold upon me,
so that I am not able to look up;
they are more than the hairs of mine head:
therefore my heart faileth me.
Vs.12
"The poles of thanksgiving and lament are so distinct in this
psalm that some divide it into two separate psalms.
This is not
necessary, since the man of God can present his lament and petition to
God, while at the same time offering his thanksgiving.
The thanksgiving
is offered (in verses 1-8). leads naturally into the lament and petition section of the
psalm (verses 11-17).
His petition is a plea for deliverance from his
enemies, but it is wider than that. He is concerned about the triumph of
all righteous people (verse 16).
1) Precedent from a Past Situation (40:1-10). 
I waited patiently for the LORD; and he inclined unto me, and heard my cry. Vs.1
2) The Merciful Rescue by God (40:1-3);
He brought me up also out of an horrible pit, out of the miry clay, and set my feet upon a rock,.. Vs.2
3) The Multiple Resources in God (40:4-5);
Many, O LORD my God, are thy wonderful works which thou hast done, and thy thoughts which are to us-ward: they cannot be reckoned up in order unto thee: if I would declare and speak of them, they are more than can be numbered. Vs.5
4) The Motivational Responses to God (40:6-10).
I have not hid thy righteousness within my heart; I have declared thy faithfulness and thy salvation: I have not concealed thy lovingkindness and thy truth from the great congregation. Vs.10
5) Prayers for a Present Situation (40:11-17).
But I am poor and needy; yet the Lord thinketh upon me: thou art my help and my deliverer; make no tarrying, O my God. Vs.17.
The sixth, seventh, and eighth verses contain a remarkable prophecy of the incarnation and sacrificial offering of Jesus Christ.
--Verse Psalms 40:6. Sacrifice and offering —The apostle, Hebrews 10:5, c., quoting this and the two following verses, says, When he (the Messiah) cometh into the world-was about to be incarnated, He saith-to God the Father, Sacrifice and offering thou wouldst not-it was never thy will
and design that the sacrifices under thy own law should be considered
as making atonement for sin they were only designed to point out my
incarnation and consequent sacrificial death: and therefore a body hast thou prepared me, by a miraculous conception in the womb of a virgin; according to thy word, The seed of the woman shall bruise the head of the serpent.
--Verse Psalms 40:7. In the volume of the book — במגלת ספר bimegillath sepher, "in the roll of the book." Anciently, books were written on skins, and rolled up. The book mentioned here must be the Pentateuch, or five
books of Moses; for, in David's time no other part of Divine revelation
had been committed to writing. This whole book speaks about Christ, and
his accomplishing the will of God, not only in "the seed of the
woman shall bruise the head of the serpent," and "in thy seed shall all
the nations of the earth be blessed;" but in all the sacrifices and sacrificial rites mentioned in the law.
--Verse Psalms 40:8. To do thy will — God willed not the sacrifices under the law, but he willed that a human victim of infinite merit should be offered for the redemption of mankind. That there might be such a victim, a body was prepared for the eternal Logos, and in that body he came to do the will of God; that is, to suffer and die for the sins of the world.
Verse Psalms 40:2. A horrible pit — Literally, the sounding pit;
where nothing was heard except the howlings of wild beasts, or the
hollow sounds of winds reverberated and broken from the craggy sides and
roof.
The miry clay — Where the longer I stayed the deeper I sank, and was utterly unable to save myself. The Syriac and Arabic
translate "The pit of perdition, and the mud of corruption." These are
figurative expressions to point out the dreary, dismal, ruinous state of
sin and guilt, and the utter inability of a condemned sinner to save
himself either from the guilt of his conscience, or the corruption of
his heart.
Set my feet upon a rock — Thou hast changed my state from guilt to pardon; from corruption to holiness; in consequence of which my goings are established. I have now power over all sin, and can walk steadily in the way that leads to God's kingdom.
Verse Psalms 40:3. A new song
— Cheerfulness and joy had long been strangers to him.
Praise for a sense of God's favor was a new song to him."
BooksOfTheBible/AdamClarke
Be pleased, O LORD, to deliver me:
O LORD, make haste to help me.
Vs.13