Dawud bin Ali narrated: Sayyidah Umm al-Fadl (may Allah be pleased with her) became pregnant in the Shi'b (during the siege of Abu Talib's valley), and the Messenger of Allah (peace and blessings be upon him) said: "I hope that she will brighten our faces with a son." So she gave birth to Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10519