The answer is: it is possible, but rare. One possible scenario is that the sky is overcast and they have no clocks, so they assume that it is still early; then the clouds clear, and they find that it is close to the time for Asr prayer.
The second condition: the attendance of forty people upon whom it is obligatory.
His statement, “The second condition: the attendance of forty people upon whom it is obligatory,” means that the second condition for the validity of Jumu‘ah is the attendance of forty people. What is meant is their attendance at both sermons and the prayer. It has previously been explained who those upon whom it is obligatory are. Thus, if thirty people upon whom it is obligatory attend the sermon but not the prayer, it is not valid; and if they attend the prayer but not the sermon, the prayer is not valid.
It has previously been explained who those upon whom Jumu‘ah is obligatory are: every male, free, legally accountable Muslim who is settled in a built-up locality no more than a farsakh from the mosque—six conditions. Therefore, all forty must possess these qualities.
If thirty-nine free men and one slave attend, it is not valid, because the slave is not among those upon whom it is obligatory, even though he completes the number of forty. Likewise, if thirty-nine settled residents and a resident traveler attend, it is not valid, because a resident traveler is not a settled resident, whereas we stipulated that he must be settled. If one woman and thirty-nine men attend, it is not valid, because she is not among those upon whom it is obligatory. And if, in a town in a land of disbelief, one hundred students gather, with none of them being from the local inhabitants, they may not establish Jumu‘ah, because they are not settled residents.
They cited the following as evidence for stipulating forty:
- Ahmad said: “The Prophet, peace and blessings be upon him, sent Mus‘ab ibn ‘Umayr to the people of Madinah. When Friday came, he led them in Jumu‘ah, and they were forty; and it was the first Jumu‘ah established in Madinah.” The response is: even if this report is authentic, it does not establish proof.