Hadith 9:98
Abu Bakr narrated to us, he said: Mu'tamir narrated to us, from Salam ibn Abi al-Dhayyal, he said: Umar ibn Abd al-Aziz wrote regarding two orphans, if they are married while they are young, that they have the choice [to accept or reject the marriage upon reaching puberty].
حدثنا أبو بكر قال نا معتمر عن سلم بن أبي الذيال قال كتب عمر بن عبد العزيز في اليتيمين إذا زوجا وهما صغيران إنهما بالخيار