Albert Barnes Commentary Psalms 70:5

"But I am poor and needy; Make haste unto me, O God: Thou art my help and my deliverer; O Jehovah, make no tarrying." — Psalms 70:5 (ASV)

But I am poor and needy - This is the same as in Psalms 40:17.

Make haste to me, O God - Hebrew, אלהים 'Elohiym. In the parallel place in Psalms 40:17, the text reads, The Lord thinketh upon me, - where the Hebrew word is not אלהים 'Elohiym — but אדני 'Adonāy (Lord). The phrase “make haste” seems to have been introduced here by design. This carries out the main idea in Psalms 40, but it turns what is stated there as a “fact” into a “petition” here.

You are my help and my deliverer ... - The end of the psalm is the same as the end of Psalms 40, except that the word Lord (Yahweh) is used here instead of “God” (אלהים 'Elohiym).

It is not possible to ascertain whether these changes were mere matters of taste or whether they were designed to adapt the psalm to some new circumstance or to the special feelings of the psalmist at the time.

There is no evidence that they are mere errors of transcribers; indeed, the changes are made in such a way that this cannot be supposed. The change of the names אלהים 'Elohiym — יהוה Yahweh — and אדני 'Adonāy — for example, is such that it must have been by design and could not have been made by copyists.

But what that design was must remain unknown. The alterations do not in any way, as far as we can understand, affect the meaning.