مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3311
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) travelled from Makkah to Madinah, not fearing anything but Allah and he shortened the prayer.
Musnad Ahmad 3334A saheeh hadeeth]