Mustadrak al-Hakim — Hadith 4125

It is narrated from al-Suddi (may Allah have mercy on him) that he related: Ishaq bin Ibrahim, the Friend of Allah (peace be upon them both), married a woman, and she conceived two boys (twins) in one pregnancy. When the time of her delivery drew near, the two boys began to fight in their mother's womb. Ya'qub (peace be upon him) wanted to be born before Aysa, so Aysa said: "By Allah, if you come out before me, I will lie crosswise in my mother's womb and kill her." At this Ya'qub (peace be upon him) held back and Aysa was born before him; then Ya'qub (peace be upon him) was born holding on to his heel. Aysa was named 'Aysa' because he disobeyed and came out before Ya'qub, and Ya'qub was named 'Ya'qub' because he was born holding on to Aysa's heel ('aqib). Although Ya'qub was the elder in the womb, Aysa disobeyed and came out first. Then the two boys grew up. Aysa was more beloved to his father (Ishaq (peace be upon him)), while Ya'qub was more beloved to his mother. Aysa was fond of hunting. Then when Ishaq (peace be upon him) grew old, his sight left him; and the narrator related a long hadith. [Mention of Yusuf bin Ya'qub (may the blessings of Allah be upon them both)]