King David reaches out to God from a place of deep distress, asking Him to replace his current sadness with joy. This plea for a gladdened spirit comes from a heavy heart, as he is presently weighed down by grief and sorrow [רד״ק, מאירי]. Beyond simply asking for relief from emotional pain, this request is deeply tied to the desire to avoid doing wrong. David asks God to bring joy to his soul by preventing him from making a terrible mistake, specifically by keeping him from killing the men of Saul. Committing such an act would permanently stain his soul and fill him with a deep, lasting sadness [אלשיך].
The foundation of this plea for joy is David's absolute reliance on God, who serves as his only source of hope and his sole support in times of trouble [ביאור שטיינזלץ, אבן עזרא]. He describes this absolute trust as an act of lifting his soul directly to God. Commentators explain this profound connection in a few complementary ways. Primarily, it represents a deep inner focus. It is the act of directing the heart completely toward God, begging Him with total devotion [רש״י, רד״ק], and actively choosing to lean on Him to carry life's heavy burdens [מצודת דוד].
Building on the importance of avoiding sin, David recognizes that he cannot truly direct his soul toward God if his inner self is damaged and flawed by wrongdoing [אלשיך]. Another approach views this lifting of the soul as presenting a gift or offering. In this sense, a person raises his soul to God as a total personal sacrifice, offering his very essence before Him just as one would present a physical offering of fat and blood [מאירי, רד״ק].