Bow to the Master

Walkthrough
It is possible to find Dravin's Bow before obtaining this quest and it will be identified as a quest item, but the quest will not be triggered until the Dragonborn actually speaks with Dravin Llanith on his farm outside Riften.

Retrieve Dravin's Bow
The bow is located in the Ratway Warrens under the city of Riften in a locked chest.

Return Dravin's Bow
Once the bow has been retrieved, the Dragonborn simply returns to Merryfair Farm and gives it to Dravin.

Beschaffe Dravins Bogen