Musnad Ahmad 1153:1326

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from 'Ata' al-Khurasani, from Yahya ibn Ya'mar, from 'Aisha, she said: A man asked her: "Did the Messenger of Allah, may Allah bless him and grant him peace, raise his voice at night when he recited?" She said: "Yes, sometimes he would raise it, and sometimes he would lower it." He said: "Praise be to Allah who has placed ease in the religion." He said: "And did he perform Witr at the beginning of the night?" She said: "Yes, sometimes he would perform Witr at the beginning of the night, and sometimes he would perform Witr at the end of it." He said: "Praise be to Allah who has placed ease in the religion."