There is no consensus regarding the interpretation of the "Spirit like a dove" comparison in Jesus' baptism (Mk 1:10). Although scholars have proposed at least fifty different interpretations of the dove comparison, no study appears to have considered Isaiah's three dove texts as the background for the Markan dove (cf. Is 38:14; 59:11; 60:8). This neglect is surprising considering the abundance of Isaianic allusions in Mark's Prologue (Mk 1:1-15), and the growing awareness that Isaiah is the hermeneutical key for both the Markan Prologue and Jesus' baptism within it. Indeed, Mark connects the dove image inseparably to the Spirit's "descent" from heaven, which alludes to Yahweh's descent in a New Exodus deliverance in Isaiah 63:19 [MT]. Furthermore, each Isaianic dove text uses the same simile, "like a dove" or "like doves," which appears in Mark 1:10, and shares the theme of lament and restoration which fits the context of Mark's baptism account. This study therefore argues that the dove image in Mark 1:10 is a symbol which evokes metonymically Isaiah's three dove texts. So the Spirit is "like a dove" not because any quality of the Spirit resembles that of a dove, but because the dove recalls the Isaianic theme of lament and restoration associated with doves in this Scriptural tradition. After discussing the Markan dove in terms of simile, symbol, and metonymy, the study examines the Isaianic dove texts in the MT and LXX and argues that they form a single motif. Next, later Jewish references to the Isaianic dove texts are considered, while an Appendix examines further dove references in Jewish and Greco-Roman literature. Finally, the study argues that the Markan dove coheres in function with the Isaianic dove motif and symbolizes the Spirit's effect upon and through Jesus by evoking metonymically the Isaianic dove texts.