Musnad Ahmad 30:718

'Abd al-Razzaq narrated to us, he said: Ibn Jurayj said: Al-'Ala' ibn 'Abd al-Rahman ibn Ya'qub informed me that Abu al-Sa'ib, the freed slave of Hisham ibn Zuhrah, informed him that he heard Abu Hurayrah say: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever performs a prayer in which he does not recite the Mother of the Qur'an, it is deficient, it is deficient, not complete." Abu al-Sa'ib said to Abu Hurayrah: "O Abu Hurayrah, I am sometimes behind the Imam." Abu al-Sa'ib said: So Abu Hurayrah squeezed my arm and said: "O Persian, recite it to yourself." I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: "Allah the Mighty and Majestic said: 'I have divided the prayer between Myself and My servant into two halves; half of it is for Me, and half of it is for My servant, and My servant shall have what he asks for.'" Abu Hurayrah said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Recite." He said: The servant says: {All praise is due to Allah, Lord of the worlds}, and Allah says: "My servant has praised Me." The servant says: {The Entirely Merciful, the Especially Merciful}, and Allah says: "My servant has extolled Me." The servant says: {Sovereign of the Day of Recompense}, and Allah says: "My servant has glorified Me." And He said: "This is between Me and My servant." The servant says: {It is You we worship and You we ask for help}. He said: "The end of it is for My servant, and My servant shall have what he asks for." He said: The servant says: {Guide us to the straight path, the path of those upon whom You have bestowed favor, not of those who have evoked [Your] anger or of those who are astray}. Allah the Mighty and Majestic says: "This is for My servant, and My servant shall have what he asks for."