The theme of faith in Mark's gospel takes its point of departure in the very first words found on the lips of Jesus. After the scene is set with information on time (‘after John was handed over’), place (‘Jesus came into Galilee’) and theme (‘preaching the gospel of God’), Jesus is quoted as declaring:

The declaration falls into two parts: a two-fold indicative stating the kingdom's advent, and a double imperative summoning a response to this event of repentance and faith.

The appearance of the kingdom of God constitutes the leitmotiv of the entire gospel. As the theme unfolds in the following narrative, it becomes apparent that Mark's concept of the kingdom of God resists easy definition. It is bound up in paradox and mystery, and is the subject of cryptic parabolic discourse (4:1–34). The underlying idea, however, seems relatively clear, especially against the backdrop of Isaianic prophecy which the author first evokes in 1:2f. Fundamentally, in Mark's account, God's kingdom represents the definitive manifestation of his ruling power to put things right in the world, to bring in the promised age of eschatological salvation. It is not primarily a spatial or a temporal category but a dynamic event: God himself is approaching ‘with strength’ (Isa 40:10 LXX; cf. Mk 1:7) to establish his dominion over sin, sickness and hostile powers.