It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that once the iqamah for the Fajr prayer was given, so I stood up to pray two rak‘ahs because I had not been able to pray them. The Prophet (peace and blessings be upon him) saw me praying and came close and said: "Will you pray four rak‘ahs for Fajr?"
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 3329