The general implication of the words
of the Prophet (God's peace and blessings be upon him), "When one of you
arrives in a mosque, he is to offer two rakas ", conveys that anyone entering a
mosque on a Friday is to offer two rakas even if the imam is delivering the
sermon. They also use the narration of Jabir
Not to pray.
The evidence of the command of paying attention to the speaker in
silence requires that the entrant is not to occupy himself with anything that
distracts him from silent attention, even if such an activity is worship.
Jabir b. 'Abdullah said that a person entered the Mosque while the Messenger of Allah (may peace be upon him) was delivering the sermon on Friday. Upon this he (the Holy Prophet) said: Have you observed prayer? He said: No. He (the Holy Prophet) said: Stand and offer the two rak'ahs. According to Qutaiba, the words are:" He said: Offer two rak'ahs."