Hadith 502600
Chapter 7: Tahajjud - كتاب صلاة الليل
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ سَعِيدَ بْنَ الْمُسَيَّبِ، كَانَ يَقُولُ يُكْرَهُ النَّوْمُ قَبْلَ الْعِشَاءِ وَالْحَدِيثُ بَعْدَهَا .
Yahya related to me from Malik that he had heard that Said ibn al-Musayyab used to say, "Sleep is disapproved of before isha and conversation after it."
Reference Muwatta Malik 502600
USC-MSA web (English) reference : Book 7, Hadith 6