Facing the Qibla in Nafl, Innovations, Praying on an Airplane or a Boat
From imamfaisal.com: https://imamfaisal.com/fiqh-of-prayer/ · Chapter: Chapter on Conditions of Prayer · Class notes: https://imamfaisal.com/wp-content/uploads/english_Ahmad_ibn_Hanbals_Treatise_on_Prayer.pdf