Once the masonry walls have been built they need to harden before you can start plastering. You should wait 28 days from the completion of the wall until you can plaster it. The cement used in plaster or mortar needs time to hydrate before it reaches its full strength and hardness.
Adding water to cement to form a water-cement paste starts a chemical reaction that makes the paste into a bonding agent. This hydration produces a stone-like substance or the hardened cement paste as we all know. The quality of hydration determines the strength of the bond in masonry and the lower permeability risks of the wall.
This hydration process is also called curing during which the mortar in the masonry wall becomes hard or solid by crystallization.
When the plaster or masonry surface drys out excessively, the structure may be under undue stress ,which the still-hydrating interior cannot withstand. This will eventually course cracks in the plaster.