Shulchan Arukh, Orach Chayim Siman 625
Can copy this into an AI, or connect the whole library to your assistant. For deeper learning, you can directly use the original seforim, sites, and apps.
בסוכות תשבו שבעת ימים וגו' כי בסוכות הושבתי את בני ישראל הם ענני כבוד שהקיפם בהם לבל יכם שרב ושמש: ומצוה לתקן הסוכה מיד לאחר י"כ דמצוה הבאה לידו אל יחמיצנה [מהרי"ל]:
Mishna Berura Yomi
On Succot we shall dwell for 7 days etc. Because on Succot I protected the children of Israel. These refer to the clouds of glory who protected them from all the intense heat and the sun of the desert. And it is a Mitzvah to begin building the Succah immediately after Yom Kippur. For if a Mitzvah that comes to one's hands, one should not delay performing it.[Maharil]