Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
The psalmist prays for speedy deliverance, Psa 70:1; prays against those who sought his life, Psa 70:2, Psa 70:3; and for the blessedness of those who sought God, Psa 70:4; urges his speedy deliverance, Psa 70:5.
The title in the Hebrew is, To the chief Musician, A Psalm of David, to bring to remembranee. There seems little sense in this title. It seems to intimate that the Psalm was written as a memorial that David had been in sore affliction, and that God had delivered him. So the Vulgate, Septuagint, Ethiopic, and Arabic. It is almost word for word the same with the five last verses of Psalm 40, to the notes on which the reader is referred.
Make haste to help me - I am in extreme distress, and the most imminent danger. Haste to help me, or I am lost.
Let them be turned backward - They are coming in a body against me. Lord, stop their progress!
That say, Aha, aha - האה האה Heach! heach! a note of supreme contempt. See on Psa 40:15 (note).
Let God be magnified - Let his glory, mercy, and kindness, continually appear in the increase of his own work in the souls of his followers!
But I am poor and needy - עני ואביון ani veebyon, I am a poor man, and a beggar - an afflicted beggar; a sense of my poverty causes me to beg.
Thou art my help - I know thou hast enough, and to spare; and therefore I come to thee.
Make no tarrying - My wants are many, my danger great, my time short. O God, delay not!