مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3570
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdur-Rahman bin Yazeed said: 'Uthman prayed in Mina with four rak’ahs and ‘Abdullah (رضي الله عنه) said: I prayed with the Prophet (ﷺ) in Mina with two rak'ah's and with Abu Bakr two rak'ahs and with ‘Umar two rak'ahs.
Musnad Ahmad 3593Its isnad is saheeh, al-Bukhari (1084) and Muslim (695)]