Is it permissible to combine prayers at home due to rain, or is combining prayers permissible only in the mosque? And what is the ruling on praying on sponge or embroidered and shiny clothes?

It is permissible to combine two prayers due to rain in order to attain the virtue of congregational prayer and avoid hardship. This permissibility ceases if either of the two reasons (virtue of congregation or avoidance of hardship) is absent. Prostration on sponge is not valid unless it is firm and dense, because one of the conditions for valid prostration is the stability of the forehead on the ground or what is connected to it. Prayer is valid with embroidered and shiny clothes, though it is disliked due to the worshiper's distraction by them.