What is the reason for the revelation of the Almighty's saying: (O you who have believed, let those whom your right hands possess and those among you who have not reached puberty ask permission of you at three times... [the verse])?

The verse was revealed because a young boy entered upon 'Umar ibn al-Khattab during his midday nap, and something of 'Umar's body became uncovered. 'Umar then wished that Allah had forbidden entry without permission during those times, and so the verse was revealed in agreement with his statement. It is also said that the reason for its revelation was the entry of an older boy upon Asma bint Marthad al-Ansariyyah. It is possible that both incidents occurred around the same time, leading to the revelation of the verse because of them.