What is the ruling on performing tayammum for the purpose of purification before sleeping when water is available and one is able to use it?

Tayammum is not prescribed except when water cannot be used, whether due to its absence or the fear of harm from using it, as Allah says: (And if you do not find water, then perform tayammum with pure earth and wipe over your faces and your hands). Eight conditions are required for tayammum: intention, Islam, sanity, discernment, istinja or istijmar (cleaning oneself after relieving oneself), the entry of the prayer time, the inability to use water (either due to its absence or the fear of harm), and that it be with pure, permissible earth that has dust. If water is available and there is no fear from using it, tayammum is not valid for prayer, tawaf, or any other act of worship that requires ritual purity.