John Calvin Commentary Psalms 63:8

"My soul followeth hard after thee: Thy right hand upholdeth me." — Psalms 63:8 (ASV)

My soul has cleaved hard after you. The Hebrew verb also means to apprehend, or follow, especially when in construction with the preposition that is joined to it here. Therefore, we could very properly translate the words as — My soul shall press or follow after you. But even if the other translation is retained, the sense is that David’s heart was devoted to God with steadfast perseverance.

The phrase, after you, is emphatic and denotes that he would follow with unwearied constancy, however long the way might be, full of hardships, and beset with obstacles, and however sovereignly God might himself seem to withdraw his presence. The latter clause of the verse can be understood as referring simply to the deliverance that he had previously mentioned receiving. He had good reason to persevere, without giving up, in following after God, when he considered that he had been preserved in safety until now by God’s hand.

However, I would understand the words as having a more extensive application, and I consider that David here speaks of the grace of perseverance, which would be given to him by the Spirit. To say that he would cleave to God with an unwavering purpose, regardless of the dangers, might have sounded like vain boasting if he had not qualified the assertion by adding that he would do this only to the extent that he was sustained by God’s hand.