مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3470
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: We travelled with the Messenger of Allah (ﷺ) between Makkah and Madinah not fearing anyone but Allah, may He be glorified and exalted, and we prayed two rak'ahs (i.e., shortened the four rak'ah prayers).
Musnad Ahmad 3493A saheeh hadeeth, its isnad is da'eef]