We explore a technique for decelerating molecules using a static magnetic field and optical pumping. Molecules travel through a spatially varying magnetic field and are repeatedly pumped into a weak‐field seeking state as they move towards each strong field region, and into a strong‐field seeking state as they move towards weak field. The method is time‐independent and so is suitable for decelerating both pulsed and continuous molecular beams. By using guiding magnets at each weak field region, the beam can be simultaneously guided and decelerated. By tapering the magnetic field strength in the strong field regions, and exploiting the Doppler shift, the velocity distribution can be compressed during deceleration. We develop the principles of this deceleration technique, provide a realistic design, use numerical simulations to evaluate its performance for a beam of CaF, and compare this performance to other deceleration methods. Escher meets Sisyphus: A deceleration technique for molecular beams is explored that relies on repeated optical pumping in a static, spatially varying, magnetic field. Molecules are pumped between weak‐ and strong‐field seeking states so that they are always climbing potential hills (see picture). The principles of this technique are developed, a design based on permanent magnets presented, and trajectory simulations used to study its performance for slowing a beam of CaF.