Sahih Al Bukhari Hadith Number 931

Narrated Jabir: A man entered the Mosque while the Prophet (peace be upon him) was delivering the Khutba. The Prophet (peace be upon him) said to him, “Have you prayed?” The man replied in the negative. The Prophet (peace be upon him) said, “Pray two rak`at.”

11  Friday Prayer
Hadith number 931
Volume no 2
Chapter: 33 (When the Imam is delivering the Khutba, a light two Rak’a Salat (prayer) (Tahayyat-ul Masjid)