But I am poor and needy - More literally, "I am afflicted and poor." The language would describe the condition of one who was afflicted and was at the same time poor; of one who had no resource but in God, and who was passing through scenes of poverty and sorrow. There were undoubtedly times in the life of David to which this language would be applicable; but it would be far more applicable to the circumstances in which the Redeemer was placed; and, in accordance with the interpretation which has been given of the other parts of the psalm, I suppose that this is designed to represent his afflicted and humble condition as a man of poverty and sorrow.

Yet the Lord thinketh upon me - The Lord cares for me; he has not forgotten me. Man forsakes me, but he will not. Man leaves me to poverty and sorrow, but, he will not. How true this was of the Redeemer, that the Lord, the Father of mercies; thought on him, it is not needful now to say; nor can it be doubted that in the heavy sorrows of his life this was a source of habitual consolation. To others also - to all his friends - this is a source of unspeakable comfort. To be an object of the thoughts of God; to be had in his mind; to be constantly in his remembrance; to be certain that he will not forsake us in our trouble; to be assured in our own minds that one so great as God is - the infinite and eternal One - will never cease to think on us, may well sustain us in all the trials of life. It matters little who does forsake us, if he does not; it would be of little advantage to us who should think on us, if he did not.

Thou art my help and my deliverer - Implying the highest confidence. See the notes at Psalm 18:2.

Make no tarrying, O my God - Do not linger or delay in coining to my assistance. The psalm closes with this prayer. Applied to the Redeemer, it indicates strong confidence in God in the midst of his afflictions and sorrows, with earnest pleading, coming from the depth of those sorrows, that God would interpose for him. The vision of the psalmist extended here no farther. His eye rested on a suffering Messiah - afflicted, crushed, broken, forsaken - with all the woes connected with the work of human redemption, and all the sorrows expressive of the evil of sin clustering upon him, yet confident in God, and finding his last consolation in the feeling that God "thought" on him, and in the assurance that He would not ultimately forsake him. There is something delightful, though pensive, in the close of the psalm. The last prayer of the sufferer - the confident, earnest pleading - lingers on the ear, and we almost seem to behold the Sufferer in the depth of his sorrows, and in the earnestness of his supplication, calmly looking up to God as One that "thought" on him when all others had forgotten him; as a last, safe refuge when every other refuge had failed. So, in our sorrows, we may lie before the throne, calmly looking up to God with a feeling that we are not forgotten; that there is One who "thinks" on us; and that it is our privilege to pray to him that he would hasten to deliver us. All sorrow can be borne when we feel that God has not forgotten us; we may be calm when all the world forsakes us, if we can feel assured that the great and blessed God thinks on us, and will never cease to remember us.

Psalm 40:17 Parallel Commentaries

"Lo, I Come": Exposition
"Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me: in burnt offerings and sacrifices for sin thou hast had no pleasure. Then said I, Lo, I come in (the volume of the book it is written of me,) to do thy will, O God." WE HAVE, in the use made of the passage by the inspired apostle, sufficient authority for applying the quotation from the fortieth psalm to our divine Lord and Savior Jesus Christ. With such a commentary, we …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 37: 1891

Eligius, Bishop of Noyon.
THE life of this pious bishop is so much the more worthy our consideration, on account of his having passed many years in the position of an ordinary citizen, before he entered on the clerical office; because his life may thus afford us a picture of the pious citizens of his time. Eligius was born at Chatelàt, a mile from Limoges, A. D. 588. His family had been Christian for many generations, and he received a pious education, [8] the result of which extended throughout his life. In his youth, …
Augustus Neander—Light in the Dark Places

The Lamb of God, the Great Atonement
Behold the Lamb of God, which taketh away the sin of the world! G reat and marvellous are the works of the LORD God almighty! We live in the midst of them, and the little impression they make upon us, sufficiently proves our depravity. He is great in the very smallest; and there is not a plant, flower, or insect, but bears the signature of infinite wisdom and power. How sensibly then should we be affected by the consideration of the Whole , if sin had not blinded our understandings, and hardened …
John Newton—Messiah Vol. 1