Musannaf Ibn Abi Shayba 27:697

Zayd ibn al-Hubab narrated to us, he said: Husayn ibn Waqid narrated to me, he said: Abdullah ibn Buraydah narrated to me, from his father, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "I heard a rustling in front of me in Paradise, so I said: 'Who is this?' They said: 'Bilal.'" So he informed him and said: "By what did you precede me to Paradise?" He said: "O Messenger of Allah, I never committed a minor impurity (hadath) except that I performed ablution, and I never performed ablution except that I saw that Allah had two rak'ahs upon me, which I would pray." He said: "By it."