Mishnah Berurah — משנה ברורה

It is fitting for everyone - The Kabbalists explained at length about the great virtue of getting up at midnight because it is very great. It is already [commonly found] printed in siddurim, how this is to be done according to the Arizal. Midnight is always exactly at the middle of the night in any place, even if the nights are long or short. It is 12 hours after midday. The time to cry for the Churban is more fitting to be just a little before midnight; and from midnight and on, one should study Torah; and at the end of the night one should ask for his needs. There are some who recite "Shomrim Laboker" at that point. If it is close to sunrise, one should say the Psalms and skip the Lamentations, and then recite "Shomrim Laboker". And after the Tikun, one should learn Mishnayos before anything else. If one is fortunate to know "Chochmat Emet" (ie. Kabbalah), this is a very favorable time. The later rabbinic authorities have an accepted tradition that from "Shichvi" to "Kumi", meaning, from the weeks that they say "Shichvi" until Tisha B'av, where they say "Kumi", one does not need to get up in the night. Some people say from Tu B'av until the 15th of Iyar one should get up in the night. Those who conduct themselves based on Kabbalah hold that one must always awaken [to say Tikun Chatzot]. A group [of men] who join together to recite Tikun Chatzot collectively - we do not stop them, and just the opposite [is true] - "In the multitude of the people is the glory of the King" (Proverbs 14:28). And even better is for them to recite the Tikun in the synagogue [itself], rather than reciting it in the room adjacent to it, for the synagogue has more sanctity, and they should also [try to] be from the first ten [men to arrive]. And one must be very very careful regarding idle chatter when they awake in the night. And one who is not able to wake up before the morning light because he is of a weak nature, or because he knows that if does wake up at the latter part of the night he will [end up] sleeping during the prayer [services], it is better [for him] to sleep as much as he needs. Nevertheless, he should be very careful to wake up one hour, or at least a half hour, before the calling of the attendant [to wake up everyone to come] to the synagogue, so that he will be able to prepare himself to pray with the congregation and with cleanliness.