Sahih Bukhari Volume 002, Book 020, Hadith Number 190.

Narated By 'Abdur Rahman bin Yazid : We offered a four Rakat prayer at Mina behind Ibn 'Affan. 'Abdullah bin Masud was informed about it. He said sadly, "Truly to Allah we belong and truly to Him we shall return." And added, "I prayed two Rakat with Allah's Apostle at Mina and similarly with Abu Bakr and with 'Umar (during their caliphates)." He further said, "May I be lucky enough to have two of the four Rakat accepted (by Allah)."