"The Messenger of Allah ﷺ prayed witr at the beginning (of the night) and at the end, and in the middle. And toward the end of his life, he settled on performing witr at the end of the night." (Using translation from Nasāʾī 1681)
«أَوْتَرَ رَسُولُ اللهِ ﷺ مِنْ كُلِّ اللَّيْلِ مِنْ أَوَّلِهِ وَآخِرِهِ وَأَوْسَطِهِ وَانْتَهَى وِتْرُهُ إِلَى السَّحَرِ»