It was narrated that Hashim bin Hashim said:
"I heard Sa'eed bin Musayyab say: 'Sa'd bin Abu Waqqas said: 'No one else became Muslim on the same day as I did; for seven days I was one-third of Islam.'"
English reference: Vol. 1, Book 1, Hadith 132
Arabic reference: Book 1, Hadith 137