How to get the Daedric Long Bow - Elder Scrolls: Morrowind
Video: How to easily get a Daedric Bow
There are a couple of places in the game to obtain the Daedric Bow but the easiest is from Maelkashishi which is a dungeon found northeast of Gnisis. You can find the Daedric Longbow on the top ledge of the Forgotten Galleries portion of Maelkashishi. In order to reach this ledge you'll need Levitate, there is a door that will take you back outside to the West Gash Region right below where the ledge with the longbow can be found.
Along with the longbow you'll also find a handful of Daedric Arrows next to the same corpse along with 3 more arrows on the ledge below you where the door that leads to the West Gash Region is. 2 will be stuck in the pillar near the door and one will be lying in front of the door itself.