Musannaf Ibn Abi Shayba 21:130

Ishaq ibn Mansur narrated to us, from Huraym, from Abd al-Rahman ibn Ishaq, from Abu Kathir, the freed slave of Umm Salamah, from Umm Salamah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said to me: "Say at the time of the Maghrib adhan: 'O Allah, this is the approach of Your night, the retreat of Your day, the voices of Your callers, and the presence of Your prayer, so forgive me.'"