“O that thou wouldst hear my voice in the morning; O Jehovah, in the morning will I direct unto thee, and I will keep watch.”
The first sentence may also be read in the future tense of the indicative mood, Thou shalt hear my prayer. But, in my opinion, the verb is rather in the optative mood, as I have translated it. Having besought God to grant his requests, he now entreats him to make haste. Some think he alludes to the morning prayers which were wont to be joined with the daily sacrifices in the temple, according to the appointment of the law. Although I do not disapprove of this opinion, yet I have no doubt but that, constrained by the weariness of a somewhat lengthened delay, he wishes his deliverance to be hastened; as if he had said, “As soon as I awaken this will be the first subject of my thoughts. Therefore, O Lord, delay no longer the help of which I stand in need, but grant immediately my desires.” The expression, To direct unto God, I take to signify the same thing as directly to approach to God. Many, as if the language were elliptical, supply the words, my prayer. But in my judgment, David rather intends to declare that he was not turned hither and thither, nor drawn different ways by the temptations to which he was exposed, but that to betake himself to God was the settled order of his life. There is, in the words, an implied contrast between the rambling and uncertain movements of those who look around them for worldly helps, or depend on their own counsels and the direct leading of faith, by which all the godly are withdrawn from the vain allurements of the world, and have recourse to God alone. The Hebrew word ערך, arac, signifies to set in order or dispose, and sometimes to dress or make fit. This sense is very suitable to the passage, in which David plainly declares it to be his determination not to be drawn away in any degree from his orderly course into the indirect and circuitous paths of error and sin, but to come directly to God. By the word, watch, he conveys the idea of hope and patience as well as of anxiety. Asצפה, tsapah, in Hebrew means, to wait for, as well as to look for, David, I have no doubt, intended to say, that after he had disburdened his cares into the bosom of God, he would, with an anxious mind, look out, as it were, like a sentinel, until it should appear, that in very deed God had heard him. No doubt, in the exercise of longing, there is always implied some degree of uneasiness; but he who is looking out for the grace of God with anxious desire, will patiently wait for it. This passages therefore, teaches us the uselessness of those prayers to which there is not added that hope which may be said to elevate the minds of the petitioners into a watch-tower.
from John Calvin’s Commentary on Psalm 5:3.