Ibrahim al-Sa'igh says: I asked Matar al-Warraq: Should a man recite 'Bismillah al-Rahman al-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful) and seek refuge from Satan, the accursed, in every rak'ah and at the beginning of every surah he begins? He said: Qatadah informed me, through Muhammad bin Sirin, from Sayyiduna Imran bin Husayn and Sayyiduna Samurah bin Jundub (may Allah be pleased with them both), who narrate from the Messenger of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "They are the two pauses (silences); a person does them inwardly: when he begins the prayer, and when he rises from the sitting after two rak'ahs."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6964