Khawât b. Jubayr – Alläh be pleased with him – said:
Sleeping in the first part of the day is ignorance, and in the middle of the day [good] character, and in the last part of the day stupidity.
Al-Bukhârî, Al-Adab Al-Mufrad. Shaykh Al-Albânî graded its chain of transmission sahîh. See Sahîh Al-Adab Al-Mufrad hadith #947.