This Surah is entitled Ar Rahman, the word with which it begins. This title, however, deeply relates to the subject matter of the Surah too, for in it, from the beginning to the end, the manifestations and fruits of Allāh's attribute of mercy and grace have been mentioned.
Period of Revelation
The commentators generally hold the view that this is a Makki Surah, though according to some traditions which have been cited on the authority of Hadrat Abdullah bin Abbas, Ikrimah and Qatadah, it was revealed at Madinah. But, firstly, there are also some other traditions from these very authorities, which contradict this view; secondly, its subject matter bears a closer resemblance with the Makki Surahs than with the Madani Surahs; rather it appears to belong to the very early Makkah period. However, there are several authentic traditions which testify that it had been revealed in Makkah itself many years before the hijra.
Musnad Ahmad contains a tradition from Hadarat Asma, daughter of Abu Bakr (may Allāh bless them both), to the effect: "I saw the Messenger of Allāh offering his Prayers in the sacred precincts of the Ka'bah facing the corner in which the "Black Stone" is fixed. This relates to the time when the Divine Command, fasda bima tumar ("So, proclaim publicly, O Prophet, what you are being commanded") had not yet been revealed. The polytheists at that time were hearing the words, Fabiayyi alaa'i Rabbi kuma tukadhdhi ban, being recited by him in the Prayer." This shows than this Surah had been sent down even before Surah AlHijr.

AlBazzar, Ibn Jarir, Ibn AlMundhir, Daraqutni (in Al Afrad), Ibn Marduyah and Ibn Al Khatib (in At Tarikh) have related, on the authority of Hadrat Abdullah bin Umar, that once the Holy Prophet (peace and blessings of Aliah be upon him) recited Surah ArRahman himself, or heard it recited before him: then he said to the people: How is it that I am not hearing from you the kind of good answer that the jinn had given to their Lord? When the people asked what it was he replied: "As I recited the Divine Words, Fa biayyi alaa'i Rabbikuma tukadhdhiban, the jinn in response would repeat the words La bi shai'in min ni'mati Rabbina nukadhdhib: 'We do not deny any of our Lord's blessings'."

A similar theme has been related by Tirmidhi, Hakim and Hafiz Abu Bakr alBazzar from Hadrat Jabir bin Abdullah. Their tradition contains these words: "When the people kept silent on hearing the Surah ArRahman, the Holy Prophet said, 'I recited this very Surah before the jinn in the night when they had gathered together to hear the Qurʾān. They responded to it better than you have. As I recited the Divine Words, Fa bi ayyi alaa'i Rabbikuma tukadhdhiban ("O jinn and men, which blessings of your Lord will you deny?") they would respond to it, saying: "O our Lord, do not deny any of your blessings Praise is for You alone" '!"
These traditions only indicate that Surah Ar Rahman had been revealed even before Surahs AlHijr and AlAhqaf. Besides, we come across another tradition which shows that it is one of those Surahs which were the earliest Revelations at Makkah. Ibn Ishaq has related this on the authority of Hadrat Urwah bin Zubair: The Companions one day said to one another: "The Quraish have never heard any one recite the Qurʾān publicly to them, and who would read out the Divine Word aloud to them? Hadrat Abdullah bin Masud said that he would. The Companions expressed the apprehension that he might be subjected to a harsh treatment and said that it should better be done by a person of a powerful family, who would protect him if the Quraish tried to subject him to violence. Hadrat Abdullah said: 'Let me alone: my Protector is Allāh.' So early next morning he went to the Ka'bah while the Quraish chiefs were sitting in their respective conferences. Hadrat Abdullah arrived at the Maqam (station of Abraham) and began to recite Surah ArRahman raising his voice as he did so. The Quraish first tried for a while to understand what he was saying. Then, when they ealized that it was the Word that Muḥammad (peace and blessings of Allāh be upon him) was representing as the Word of God, they fell upon him and began to hit him in the face. But Hadrat Abdullah was not deterred: he continued to receive the slaps and to read the Qurʾān as long as he could. At last, when he returned with a swollen face, the Companions said that they apprehended the same. He replied: 'God's enemies were never so light for me as they were today. If you say I'll recite the Qurʾān to them again tomorrow.' They all said, 'No, you have done enough; you have made them listen to what they didn't want to hear.'" (Ibn Hisham, vol. 1, p. 336)