Sahih Bukhari
Companions of the Prophet
Volume: 005 / Book Number: 057 / Hadith Number: 115
Narrated Al-Qasim bin Muhammad:
Once 'Aisha became sick and Ibn 'Abbas went to see her and said, "O mother of the believers! You are leaving for truthful fore-runners i.e. for Allah's Apostle and Abu Bakr.