Musnad Ahmad 28:416

'Abd al-Razzaq narrated to us, I heard al-Muthanna ibn al-Sabbah saying: 'Amr ibn Shu'ayb informed me, from his father, from 'Abdullah ibn 'Amr ibn al-'As, that the Prophet (peace and blessings of Allah be upon him) decreed that: "The woman has more right to her child as long as she does not marry."