Heading.
For the Chief Musician. A Psalm to/for David.
This Psalm is offered to the person responsible for the sacred music, or the choirmaster, and is of the Davidic collection. ‘To (or ‘for') David' may indicate that it was dedicated to David, written for the Davidic house, or even written by David himself.
The Psalm opens with David bewailing an illness which has left him in a weak state, and declaring that those who have consideration for him in that state will be blessed by YHWH. Indeed, he declares that it is YHWH Who will support him on his sickbed, and is in process of restoring him (‘has turned his lying down in his sickness').
He frankly admits that his suffering is partly due to his sinfulness, and asks for God's mercy to be shown to him, but at the same time he bewails the fact that his enemies are taking advantage of the situation and are speaking against him, hoping for his death. They come to see him, as befits a king, but it is clear that it is all a false front, and is simply so that they can talk glibly to him, and then take lying tales about his situation to the outer world, where there is much whispering and expectation of his death.
What saddens him most is that even one who was close to him, whom he had trusted, and who had eaten bread with him, had proved false.
He prays that YHWH will raise him up from his sickbed, and enable him to requite himself on such enemies. Indeed he is so certain that this will be so that he considers that it demonstrates that YHWH delights in him, something further proved by the assurance that he has that YHWH will not allow his enemies to triumph over him. And he closes the Psalm by expressing his confidence that God will uphold him in his integrity, and will indeed set him before His face for ever.
Many relate it to the machinations and plottings of Absalom as being at a time when David was going through a severe illness. Such an illness would explain why he was caught so totally unawares. The treacherous friend is then seen as being Ahithophel. But the very dedication of the Psalm to the Chief Musician gives it a ‘universal' application to believers.