Slavery was a significant part of society within the seventh-century Arabian context of the Qur'an. In this context, Q. 24:33, which has been universally interpreted by Muslim exegetes as the basis for a contract of mukātaba (‘indenture’) that allows slaves to work to pay for their freedom, is a particularly intriguing verse. This article examines the exegesis of Q. 24:33 against the background of the first two centuries of Islam, examining the way that its ambiguous language was interpreted in the light of socio-economic change and diverse theologico-political circles of scholarship. It is argued that an initially dominant emancipatory reading of the verse as an obligation within early Medina is preserved for over a century in Mecca, finding a home in Basran Ibāḍī scholarship of the late second/eighth century. In contrast, the dominant proto-Sunnī approach (and related proto-Zaydī tradition), centred in Iraq, adopts the formerly minority opinion that the mukātaba contract is merely permissible. By examining related legal questions, it is concluded that this shift in commentary on Q. 24:33 from the first/seventh to the second/eighth centuries reflects a broader change in the conception of the slave: from a valid economic actor on a continuum of servitude, to an item of property.