Why did Prophet Muhammad (saw) feel anxious that the people would not be able to carry out the night prayer (Qiyam)?
 Narrated 'Ursa:                     That he was informed by `Aisha, "Allah's Apostle went out in the middle of the night and prayed in the mosque and some men prayed behind him. In the morning, the people spoke about it and then a large number of them gathered and prayed behind him (on the second night). In the next morning the people again talked about it and on the third night the mosque was full with a large number of people. Allah's Apostle came out and the people prayed behind him. On the fourth night the Mosque was overwhelmed with people and could not accommodate them, but the Prophet came out (only) for the morning prayer. When the morning prayer was finished he recited Tashah-hud and (addressing the people) said, "Amma ba'du, your presence was not hidden from me but I was afraid lest the night prayer (Qiyam) should be enjoined on you and you might not be able to carry it on." So, Allah's Apostle died and the situation remained like that (i.e. people prayed individually). "