It is narrated from Sayyiduna Shaddad bin Aws (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever recites a surah of the Qur'an when he lies down on his bed, an angel is appointed over him who guards him until he wakes, whenever he wakes." And I also heard him (peace and blessings be upon him) say: "I ask You for steadfastness in the matter (of religion), I ask You for firm resolve upon right guidance, I ask You for gratitude for Your blessing, I ask You for excellence in Your worship, I ask You for a sound heart and a truthful tongue, I seek Your forgiveness for what You know, and I seek refuge in You from the evil that You know."
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7145