Abu Darda' reported Allah's Apostle (ﷺ) as saying:Is any one of you incapable of reciting a third of the Qur'an in a night? They (the Companions) asked: How could one recite a third of the Qur'an (in a night)? Upon this he (the Holy Prophet) said: "'Say: He is Allah, One' (Qur'an. cxii) is equivalent to a third of the Qur'an
This hadith has been narrated by Qatada with the same chain of transmitters in these words:He (the Messenger of Allah) said: Allah divided the Qur'an into three parts, and he made:" Say: He, Allah is One." one part out of the (three) parts of the Qur'an