Muwatta Imam Malik Book of Tahajjud, Hadith 9

Yahya related to me from Malik from Said ibn Abi Said al-Maqburi from Abu Salama ibn Abd ar-Rahman ibn Awf that he asked A'isha, the wife of the Prophet ﷺ what the prayer of the Messenger of Allah ﷺ was like during Ramadan. She said, "The Messenger of Allah ﷺ did not go above eleven rakas in Ramadan or at any other time. He prayed four - do not ask me about their beauty or length. Then he prayed another four - do not ask me about their beauty and length. Then he prayed three."
A'isha continued, "I said, 'Messenger of Allah, are you sleeping before you do the witr?' He said, A'isha, my eyes sleep but my heart does not sleep.' "

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ سَعِيدِ بْنِ أَبِي سَعِيدٍ الْمَقْبُرِيِّ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، أَنَّهُ سَأَلَ عَائِشَةَ زَوْجَ النَّبِيِّ ﷺ كَيْفَ كَانَتْ صَلاَةُ رَسُولِ اللَّهِ ﷺ فِي رَمَضَانَ فَقَالَتْ مَا كَانَ رَسُولُ اللَّهِ ﷺ يَزِيدُ فِي رَمَضَانَ وَلاَ فِي غَيْرِهِ عَلَى إِحْدَى عَشْرَةَ رَكْعَةً يُصَلِّي أَرْبَعًا فَلاَ تَسْأَلْ عَنْ حُسْنِهِنَّ وَطُولِهِنَّ ثُمَّ يُصَلِّي أَرْبَعًا فَلاَ تَسْأَلْ عَنْ حُسْنِهِنَّ وَطُولِهِنَّ ثُمَّ يُصَلِّي ثَلاَثًا فَقَالَتْ عَائِشَةُ فَقُلْتُ يَا رَسُولَ اللَّهِ أَتَنَامُ قَبْلَ أَنْ تُوتِرَ فَقَالَ " يَا عَائِشَةُ إِنَّ عَيْنَىَّ تَنَامَانِ وَلاَ يَنَامُ قَلْبِي " .