al-Hajjaj (49) arranged these, requiring them to be sworn upon at the time of the bay'ah (oath of allegiance) and for important matters concerning the Sultan. The bay'ah during the time of the Messenger of God, may God bless him and grant him peace, and his Rightly Guided Caliphs, was by shaking hands. But when al-Hajjaj came to power, he arranged them as oaths that encompass swearing by God, divorce, manumission, and giving wealth in charity. Whoever does not know these (oaths), his oath is not established by anything contained within them, because this is not explicit in swearing, and allusion (kinayah) is not valid without intention, and one who does not know a thing cannot possibly intend it. If he knows them but does not intend to establish an oath with what is in them, [it is not valid] either, for the reason we have mentioned. Whoever knows them and intends the oath with what is in them, it is valid regarding divorce and manumission, because an oath by them is established by allusion. As for what is beyond that, such as an oath by God Almighty and other than divorce and manumission, the Qadi said here: His oath is also established because it is an oath, so it is established by the intended allusion, like the oath of divorce and manumission. He said in another place: An oath by God is not established by allusion. This is the school of al-Shafi'i, because expiation is only rendered incumbent for it due to what is mentioned therein of the Great, Respected Name of God, and that is not present in allusion. And God Almighty knows best.

Book of Vows (Al-Nudhur)