Make haste - These words are supplied by our translators. The first word in Psalm 40:13, rendered "be pleased," is here omitted in the original. The psalm in the Hebrew begins abruptly - "O God, to deliver me," - leaving the impression that this is a fragment - a fragment commencing without even the care necessary to make the grammatical construction complete.
O God - Hebrew, אלהים 'Elohiym. In the corresponding place in Psalm 40:13 the word is "Yahweh." Why the change was made is unknown. The remainder of the verse is the same as in Ps. 40.

Make haste to help me - I am in extreme distress, and the most imminent danger. Haste to help me, or I am lost.

"To the chief Musician, [A Psalm] of David, to bring (a) to remembrance." [Make (b) haste], O God, to deliver me; make haste to help me, O LORD.
(a) Which might put him in remembrance of his deliverance.
(b) He teaches us to be earnest in prayer even though God seems to delay: for at his time he will hear us.

Make haste, O God, to deliver me,.... The phrase, "make haste", is supplied from the following clause in Psalm 40:13; it is, "be pleased, O Lord", or "Jehovah". The Targum renders it, "to deliver us"; very wrongly;
make haste to help me, O Lord; See Gill on Psalm 22:19.

This psalm is almost the same as the last five verses of Psalm 40. While here we behold Jesus Christ set forth in poverty and distress, we also see him denouncing just and fearful punishment on his Jewish, heathen, and antichristian enemies; and pleading for the joy and happiness of his friends, to his Father's honour. Let us apply these things to our own troubled circumstances, and in a believing manner bring them, and the sinful causes thereof, to our remembrance. Urgent trials should always awake fervent prayers.

We see at once at the very beginning, in the omission of the רצה (Psalm 40:14), that what we have here before us is a fragment of Ps 40, and perhaps a fragment that only accidentally came to have an independent existence. The להצּילני, which was under the government of רצה, now belongs to הוּשׁה, and the construction is without example elsewhere. In Psalm 70:3 (= Psalm 40:15) יחד and לספּותהּ are given up entirely; the original is more full-toned and soaring. Instead of ישׁמּוּ, torpescant, Psalm 70:4 has ישׁוּבוּ, recedant (as in Ps 6:11, cf. Psalm 9:18), which is all the more flat for coming after יסגו אחור. In Psalm 70:4, after ויאמרים the לי, which cannot here (cf. on the contrary, Psalm 35:21) be dispensed with, is wanting.