«مانع يمنع ابتداء الحكم، كالبيع بشرط الخيار»
A third kind obstructs the initial operation of a ruling, illustrated by a sale made subject to a stipulated option (khiyar).
The sale may have been entered into, but a legally operative option affects the immediate transfer or establishment of ownership in the relevant Hanafi cases. The focus is the beginning of the legal effect, not necessarily the prior existence of the transaction.
Different options and parties have different consequences; the example is not a universal formula for every optional sale.