How and when Tayammum should be performed? When we are sick, and cannot get up from bed for even Tayammum, can Salaat be somehow performed lying down? Is there an example from the prophet’s life?

If a person fears his sickness will increase or his cure will be delayed by
using water, then only he may make Tayammum. This could be done in even
though it be with the assistance of somebody.

Salaat may be performed lying down only if one is unable to even sit and
read the Salaat. This is done by lying on your back and placing a pillow
behind your head, thereby, facing towards the Qibla and raising the knee if
possible. (Tahtaawi pg.234)

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai