Ramadan; ayat al kursi........?

once a Sahabi was acting as watchman at the BAIT UL maal , two days shaitan came and lie and got some food ,on the third day the Prophet asked how was your company ,the sahabi said ;he was a poor fellow ,the Prophet said he lied and will come again ,on the third night the Sahabi caught him and said i will not release you , Shaitan said : i will tell you something that will guard you against the devil if you read it , and said read AYAT ul KURSI , in the morning the Prophet asked how was your company he replied ,He relate this to me ,the Prophet said , do you know who he was ? no was the reply , he was shaitan even he is a liar ,he spoke the truth with you