What should a worshiper do if he enters the mosque while the Imam is delivering the Friday sermon: should he pray or sit down? And is it permissible for the Imam to shout at the worshiper and tell him, "Sit down and do not pray; do you not see me delivering the sermon"?

It is recommended for one who enters on Friday while the Imam is delivering the sermon to pray two light rak'ahs. The Imam should not forbid anyone from doing so, because the Prophet, peace and blessings be upon him, commanded praying them at this time. As for the preacher speaking for a need, it is permissible.