Narrated Abu Musa:
Abu 'Amir was hit with an arrow in his knee, so I went to him and he asked me to remove the arrow. When I removed it, the water started dribbling from it. Then I went to the Prophet and told him...
In the Name of Allah we enter, in the Name of Allah we leave, and upon our Lord we depend [then say As-Salaamu 'Alaykum to those present].
Info: Abu Dawud 4/325. Muslim {Hadith no. 2018) says that one should mention the Name of Allah when entering the home and when beginning to eat; and that the devil, hearing this, says: "There is no shelter for us here tonight and no food".