Have respect unto me. As the flesh is ever ready to suggest to our minds that God has forgotten us, when he ceases to manifest his power in aiding us, David here follows the order which nature dictates, in asking God to have respect unto him, as if he had altogether neglected him before. Now, it appears to me that the words might be explained thus: Have respect unto me, in order to pity me. He accounts it at once the cause and the source of his salvation to be regarded of God; and then he adds the effect of it: for as soon as God, of his own good pleasure, shall vouchsafe to regard us, his hand also will be ready to help us. Again, in order to excite the compassion of God, he sets forth his own misery, expressly stating that he is alone, that is to say, solitary; [1] and then he describes himself as poor. There can be no doubt that, in speaking thus, he alludes to the promises in which God declares that he will be always present with the afflicted and oppressed, to aid and help them.

Footnotes

1 - The Hebrew word here used is ychyd, yachid, unus, one, which is not infrequently put, as in this place, for a solitary and desolate person. David was now deserted, desolate, and destitute of all help. The word is used in the same sense in Psalm 22:20, and 35:17

Turn thee unto me - Rather, the Hebrew means: "look upon me." The idea, however, is that the face of God was, as it were, turned in another direction, or that He was not attentive to him; and he prays that He would turn and behold him; that He would see him in his trouble.
And have mercy upon me - The psalmist seems to have felt that if God would look upon him he would pity him. He would see his case to be so sad that He would show him compassion - as, when we see an object of distress, "the eye affects the heart."
For I am desolate - The word here rendered "desolate" - יחיד yâchı̂yd - means properly "one alone, only;" and then, one who "is alone," or who is solitary, forsaken, wretched. There is no deeper sadness that ever comes over the mind than the idea that we are alone in the world; that we do not have a friend; that no one cares for us; that no one is concerned about anything that might happen to us; that no one would care if we were to die; that no one would shed a tear over our grave.
And afflicted - In what way we do not know. David, however, was very often in circumstances when he could use this language. The other parts of the psalm show that the "affliction" to which he here refers was that which arose from the recollection of the sins of his early life, and from the designs and purposes of his enemies.

Turn thee unto me - Probably the prayer of the poor captives in Bablyon, which is continued through this and the remaining verses.

Turn thee unto me, and have mercy upon me,.... Or "look unto me", or "upon me" (f); which suggests that the Lord had turned himself, and hid his face from him; and expresses a desire that he would look upon him with a look of love and mercy, and arise to help and deliver him out of the hands of his enemies; he pleads no merits nor works of righteousness of his, but casts himself upon the mercy of God;
for I am desolate and afflicted; or "alone and poor" (g); not that he was quite alone, and had none with him; for though he was obliged to quit his palace, and the city of Jerusalem, yet he was accompanied by his servants, and a large number of his people; and could not be poor, in a literal sense, being king of Israel; yet he put no trust in men, nor in riches, but wholly depended on the Lord, as if he had none with him, nor anything to subsist with: and his case was indeed very deplorable, and called for pity and assistance; his own son was risen up against him, and the hearts of the men of Israel went after him; and he was obliged to flee from the city, and leave his house and family.
(f) "respice ad me", Montanus, Musculus, Junius & Tremellius, &c. (g) "solitarius et pauper", Junius & Tremellius; "et miser", Gejerus, Michaelis; so Ainsworth.

A series of earnest appeals for aid because God had seemed to desert him (compare Psalm 13:1; Psalm 17:13, &c.), his sins oppressed him, his enemies had enlarged his troubles and were multiplied, increasing in hate and violence (Psalm 9:8; Psalm 18:48).

The rendering "regard me," so far as פּנה אל means God's observant and sympathising turning to any one (lxx ἐπιβλέπειν), corresponds to Psalm 86:16; Leviticus 26:9. For this he longs, for men treat him as a stranger and refuse to have anything to do with him. יחיד is the only one of his kind, one who has no companion, therefore the isolated one. The recurrence of the same sounds עני אני is designedly not avoided. To whom could he, the isolated one, pour forth his affliction, to whom could he unveil his inmost thoughts and feelings? to God alone! To Him he can bring all his complaints, to Him he can also again and again always make supplication.