This Psalm is the first appearance of the familiar introduction "Mizmor l'Dovid" (a song of David). The Talmud in Pesachim (117a) tells us that when a Psalm starts with that phrase, it means that G-d's "spirit" rested on David, inspiring him to sing the song. The converse introductory phrase, "l'Dovid Mizmor" (of David, a song) indicates that David sang the song, which then caused G-d's "spirit" to rest upon him.