بِسْـمِ اللهِ وَلَجْنـا، وَبِسْـمِ اللهِ خَـرَجْنـا، وَعَلـى رَبِّنـا تَوَكّلْـن (ثم ليسلم على أهله.
Bismillāhi walajnā, wa bismillāhi kharajnā, wa `ala Rabbinā tawakkalnā
In the Name of Allah we enter , in the Name of Allah we leave , and upon our Lord we depend [then say As-Salāmu `Alaykum to those present].
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."