hold fast

verb2

1. •
   To stubbornly resist assault, pressure or opposition, either physically or mentally.

   • If we take science as our sole guide, if we accept and hold fast that alone which is verifiable, the old theology must go. — 1900
2. •
   A formal command to a ship's crew to grasp and hold on to a solid fitting, such as ropes or rails, to avoid being swept overboard, especially during a storm.

   • All hands...hold fast!