I asked 'Aishah: When would the Messenger of Allah ﷺ observe the witr prayer ? She replied: Any time he observed the witr, sometimes in the early hours of the night, sometimes at midnight and sometimes towards the end of it. But he used to observe the witr just before the dawn when he died.
قُلْتُ لِعَائِشَةَ مَتَى كَانَ يُوتِرُ رَسُولُ اللَّهِ ﷺ قَالَتْ كُلَّ ذَلِكَ قَدْ فَعَلَ أَوْتَرَ أَوَّلَ اللَّيْلِ وَوَسَطَهُ وَآخِرَهُ وَلَكِنِ انْتَهَى وِتْرُهُ حِينَ مَاتَ إِلَى السَّحَرِ
he asked Aishah about the Witr of the Prophet. She said: "He would perform Witr during all of the night; (either) its beginning, its middle, or its end. So when he died, his Witr ended, during the approachof As-Sahar."
عَنْ وِتْرِ رَسُولِ اللَّهِ ﷺ فَقَالَتْ مِنْ كُلِّ اللَّيْلِ قَدْ أَوْتَرَ أَوَّلِهِ وَأَوْسَطِهِ وَآخِرِهِ فَانْتَهَى وِتْرُهُ حِينَ مَاتَ إِلَى السَّحَرِ
“I asked ‘Aishah about the Witr of the Messenger of Allah ﷺ. She said: ‘He prayed Witr at every part of the night, at the beginning, in the middle and at the end, when he died (he would perform it) just before dawn.’” (Using translation from Ibn Mājah 1185)
عَنْ وِتْرِ رَسُولِ اللَّهِ ﷺ فَقَالَتْ «كُلُّ اللَّيْلِ قَدْ أَوْتَرَ رَسُولُ اللَّهِ ﷺ أَوَّلُهُ وَأَوْسَطُهُ فَانْتَهَى وِتْرُهُ حِينَ مَاتَ إِلَى السَّحَرِ»