One of the mantras, which we usually recite before going to bed is,
Ramaskandam Hanomantham Vynatheyam Vrukodharam
Shayanesha Spatenithyam Dhuswapnam Thasyanashyathi
which is a prayer to Hanuman, Garuda and Bheema to prevent bad dreams.
My question is, why exactly do we pray these 3 gods in particular and which religious text it is mentioned in?