Revealed in Makkah

The reason for the revelation of this Surah as by Ikhrimah is ” When the Jew said, ‘We worship Uzayr,the son of Allah, and the Christians said,’We worships the Messiah, the son of Allah, and the Zoroastrians said,’We worship the sun and the moon, and the idolators said, ‘We worship idols’, ‘Allah revealed to HIS Messenger S.A.S - “Say , He is Allah, One” (Surah Al-Ikhlas)meaning He is the one, the singular. Who has no peer, no assistant, no rival, no equal  and none comparable to HIM. This word Al-Ahad cannot be used for anyone in affirmation except Allah the Mighty and Majestic, because HE is perfect in all HIS attributes and actions.

Al-Bukhari recorded from Abu-Sa’id , may Allah be pleased with him, that the Messenger of Allah S.A.S said to his companions, “Is anyone of you not able to recite a third of the Quran in a single night ?” .This was something which was difficult for them and they said, ‘Which of us is able to do that, O Messenger of Allah?’ So He replied, ” Allah is the One, As- Samad (Surah Al-Ikhlaas)” is a Third of the Quran.

Imam Malik bin Anas recorded from ‘Ubayd bin Hunayn that he heard Abu Hurayrah saying, ‘I went out with prophet S.A.S and he heard a man reciting ‘Say : He is Allah, the One.; So the Messenger of Allah said, “It is obligatory”. I asked, ‘What is obligatory ?’ He replied, “Paradise“

Al-Bukhari recorded from Aishah R.A.A that whenever the prophet S.A.S would go to bed every night, he would put his hands together and blow into them. Then he would recite into them Suarah Al-Ikhlaas, Sarah Al-Falaq and Surah An-Nas. Then He would wipe whatever He was able to of His body with His hands. He would begin wiping His head and face with them and the front part of His body. He would do this for three times.

Abdullah ibn Imam Ahmad recorded from Mu’adh bin Abdullah bin Khubayb , who reported that his father said,’ We became thirsty and it became dark while we were waiting for the Messenger of Allah S.A.S to lead us in prayers. Then, when he came out he took me by my hand and said, “Say”, Then He was silent. Then he said again, “Say” So i asked, ‘What should i say?’ He said, ” Say: He is Allah, the One, and the other two surahs of refuge ( Al-Falaq and An-Nas) when you enter upon evening and the morning three times each. They will be sufficient for you two times every day.”

Source: Tafsir Ibn Kathir