If A Person Enters While The Imam Is Delivering The Khutbah Sunan Abi Dawud 1116
Translation
Jabir and Abu Salih reported on the authority of Abu Hurairah
Sulaik al-Ghatafani came while the Messenger of Allah (ﷺ) was delivering the sermon, and he said to him: "Have you prayed anything?" He said: "No." He said: "Pray two rak'ahs and make them brief."