141:3 The fourteenth of Adar is Purim. If Purim falls on a Sunday, the Fast of Esther is held on the Thursday prior. If there is a bris that day, the meal is held at night but the sandek and the baby’s father may eat during the day(, as may the mohel and the baby’s mother – Shaar HaTziyon 686:15). They do not have to make up the fast on Friday but if another person forgot and ate on Thursday, he must fast on Friday.
141:4 One should wear Shabbos clothes to shul in the evening in honor of the Megillah. When returning from shul, one should come home to lit candles, a set table, and made beds. In the maariv, after Shemoneh Esrei, we recite the full kaddish including the line “tiskabeil,” after which the Megillah is read. After that, we say “v’Atah Kadosh” from Psalm 22, which alludes to Esther. Verse 3 says, “My G-d, I call upon You by day…and by night.” The Talmud (Megillah 4a) uses this verse to support the idea that the Megillah must be read at night and again during the day. This verse is followed in the Psalm by “v’Atah Kadosh.” After that, full kaddish is recited without “tiskabeil.” On Saturday night, we say “Atah chonantanu,” “v’Atah Kadosh,” full kaddish without “tiskabeil,” havdalah over a cup(, vayitein l’cha – Mishnah Brurah 693:2) and, finally, Aleinu.