question #3 Sahih al-Bukhari 931, Book 11, Hadith 55 : What should one do if they enter the mosque while the sermon is being delivered and have not yet prayed?

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