It is narrated from Sayyiduna al-Hasan bin Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever recites Ayat al-Kursi after the obligatory prayer remains under the protection of Allah until the next prayer."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2720