996. Mourning on Purim

141:19 If a congregation does not have a Megillah that is completely kosher, but it is written according to halacha and is only missing some words in the middle, since there is no one topic missing in its entirety, one may read from it with the brachos. The reader then inserts the missing words from memory, or someone prompts him from a printed copy of the text. If there is no Megillah there at all, or if it is missing a complete topic, or if there are missing words at the beginning or the end, then each person just reads the Megillah to himself from a printed book, without brachos. (Our printed books do not fulfill the mitzvah but it is appropriate to read the Megillah from them in such a case so that the mitzvah not be forgotten - Mishnah Brurah 691:27.) If an individual only has a non-kosher Megillah, he reads from it without reciting the brachos.

141:20 A mourner during the week of shiva observes all the laws of mourning and is forbidden to see celebrations of any kind. On Purim, he may wear shoes and sit on a chair because to act otherwise would be considered public mourning, which is not done on Purim. In the evening, it would be best to get a minyan to read the Megillah in his home. If this is not possible, then the mourner should daven at home, then go to shul to hear the Megillah. If Purim falls on a Saturday night, he should go to the shul after shalosh seudos while it is still day. In the morning, he goes to shul both for services and to hear the Megillah. (Even if he had a minyan in his home, the mourner should still go to shul to hear the Megillah by day - MB 696:16.)