Surah Ar-Rahman(The Beneficent) is chapter no. 55 of The Holy Quran.
Abdullah Ibn Mas'ud (radiAllahu anhu) reported that the Prophet (SalAllahu alayhi waalihi wasalam) said, 'Everything has an adornment, and the adornment of the Qur'an is Surah ar Rahman'
[Bayhaqi in Shuab al Eiman]
The Prophet (SalAllahu alayhi waalihi wasalam) went to the companions and recited Surah ar Rahman but they were all quiet. He told them that he went to the jinn and recited it to them and they were responsive. And when he would recite the verses 'And which of the favours of the Lord will you deny' the jinn would respond 'There is nothing among your bounties that we can deny, all praise belong to Allah'
[Tirmidhi, Ibn al Mundhir, Al Adhama & Hakim 2/474]
