Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated: The iqamah for prayer was given, but I had not yet performed the two rak‘ahs (Sunnah) before the Fajr prayer (after the salam), so I stood up and began to pray them. The Prophet (peace and blessings be upon him) passed by me and said: "Will you pray four rak‘ahs for the Fajr prayer?" Salih (the narrator) was asked: Who said this? He replied: The Noble Prophet (peace and blessings be upon him) did.
Hadith Referenceمسند اسحاق بن راهويه / كتاب الصلوٰة / 197
Hadith Takhrij«مسند احمد : 354/1 . قال شعيب الارناوط : اسناده حسن .»
Explanation & Benefits
Hafiz Abdush Shakoor Tirmidhi
Benefits: It is understood that if one is unable to perform the Sunnah prayers of Fajr before the congregational prayer, then there is no harm in performing them after the congregation.