Abu Sufyan narrates from Jabir bin Abdullah (may Allah be pleased with them both) that Sulayk al-Ghatafani came while the Messenger of Allah (peace and blessings be upon him) was delivering the Friday sermon. The Prophet (peace and blessings be upon him) said: "Have you prayed two rak'ahs?" He said: No. He (peace and blessings be upon him) said: "Stand up and pray two light rak'ahs." And he said: "When any of you comes while the imam is delivering the sermon, let him pray two light rak'ahs."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5692