Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said: "When the iqamah for the prayer has been called, there is no prayer except the obligatory one." It was said: O Messenger of Allah, not even the two rak'ahs of Fajr? He (peace and blessings be upon him) said: "No, not even the two rak'ahs of Fajr."
Abu Ahmad (Ibn Adi) said: I do not know anyone who mentioned this addition in its text other than Yahya bin Nasr, from Muslim bin Khalid, from Amr. It has also been reported from Ahmad bin Sayyar from Nasr bin Hajib, which is an error. Nasr bin Hajib al-Marwazi is not strong, and his son Yahya is likewise. The authentic hadiths we have cited as evidence are sufficient without this addition.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4550