Jamrah is a pillar that the pilgrim pelts with pebbles. There are three such pillars: Al-Jamrah Al-Ula [The first stone pillar], Al-Jamrah Al-Wusta [The second (middle) stone pillar], and Jamrah Al-`Aqabah [The last and biggest stone pillar].
Explaining this in detail, the late Sheikh Ibn `Uthaymeen, a prominent Saudi Muslim scholar, issued the following fatwa:
The time for throwing Jamrat Al-`Aqabah on the day of `Eid, for those who are able to do it, is from sunrise on the day of `Eid, and for those who are weak and unable to cope with the crowding—women and children—the time is from the end of the night. Asma’ bint Abi Bakr (may Allah be pleased with her) used to watch out for moonset on the eve of `Eid, and when it had set, she would go from Muzdalifah to Mina and throw the Jamrah. The end of the time for throwing the Jamrah is sunset on the day of `Eid. If there is too much crowding and a person is far away from the Jamrah and wants to delay it until night time, there is nothing wrong with that, but he should not delay it until dawn on 11 Dhul-Hijjah.
With regard to throwing the Jamarat on the Days of Tashreeq (the 11, 12, and 13 Dhul-Hijjah), that starts after the sun has passed its zenith, i.e., midday when the time for Zhuhr begins, and lasts until nighttime. If it is too difficult because of overcrowding, there is nothing wrong with throwing the Jamarat at night, until dawn.
It is not permissible to throw the Jamarat on the eleventh, twelfth, and thirteenth before midday, because the Prophet (peace and blessings of Allah be upon him) did not throw them until after midday, and he said to the people: “Learn from me your rituals (of Hajj).” The fact that the Prophet (peace and blessings be upon him) delayed throwing the Jamarat until this time, even though it was very hot, and did not do it earlier in the day when it is cooler and easier, indicates that it is not permissible to throw the Jamarat before this time. This is also indicated by the fact that the Prophet (peace and blessings be upon him) used to throw them from the time when the sun passed its zenith before he prayed Zhuhr. This indicates that it is not permissible to throw the Jamarat before the sun passes its zenith; otherwise doing that would be better so that one could pray Zhuhr when its time began, because it is better to pray when the time for that Prayer begins. The point is that the evidence indicates that throwing the Jamarat on the Days of Tashreeq is not permissible before the sun has passed its zenith.
Throwing Jamrat Al-`Aqabah on the day of `Eid ends when dawn comes on the eleventh, and for the weak and others who cannot cope with the crowding, it starts from the end of the night.
With regard to throwing Jamrat Al-`Aqabah on the Days of Tashreeq, as with the other two pillars, it is to be done from when the sun passes its zenith (the beginning of the time for Zhuhr Prayer) and ends at dawn the following day, unless it is the last of the Days of Tashreeq, in which case throwing should not be done during the night because that is now the fourteenth of the month. The Days of Tashreeq end at sunset on the thirteenth. However, throwing during the day is better unless—because of the large numbers of pilgrims and their thoughtless attitude towards one another —one fears death, harm, or unbearable hardship, in which case it is permissible to throw the Jamarat at night and there is nothing wrong with that. If a person throws them at night even though he does not fear these things, there is also no harm in that, but it is better to be on the safe side in this matter and not throw them at night unless there is a need to do so.