By the One in Whose Hand my soul is, it is equal to one-third of the Qur’an

Abu Sa‘īd al-Khudri (may Allah be pleased with him) mentioned that a man heard another reciting the Surah: {Say, “He is Allah, the One”} repeatedly throughout the night, without adding anything else. The next morning, he came to the Messenger of Allah (may Allah's peace and blessings be upon him) and mentioned that to him, as if the questioner thought it was not enough.

Thereupon, he (may Allah's peace and blessings be upon him) swore by way of confirmation: By the One in Whose Hand my soul is, it is equal to one-third of the Qur’an.