question #3 Sahih Muslim 1165e, Book 13, Hadith 271 : Why is it important to maintain diligence in worship during the last week of Ramadan?

Seek it (Lailat-ul-Qadr) in the last (ten nights). If one among you shows slackness and weakness (in the earlier part of Ramadan), it should not be allowed to prevail upon him in the last week.