What is the determining factor for assessing the required form of expiation when the ability to pay changes between the time of obligation and the time of performance, specifically concerning the option to transition from fasting to manumission?
General Chapter
Al-Mughni
Book of Zihar
Primary text
If the obligation is determined by the state at the time the obligation arises, and a person begins fasting due to inability, he is not required to switch to manumission even if he later gains the means for it, provided he has already commenced the substitute act (fasting). This ruling is without disagreement in the madhhab and is supported by the opinions of Al-Sha'bi, Qatadah, Malik, Al-Awza'i, Al-Layth, Al-Shafi'i, Abu Thawr, and Ibn al-Mundhir. However, if a person is able to transition to manumission after initially being poor and before commencing the fast, he may choose to do so and it suffices, unless the oath-breaker was a slave at the time of the breach, in which case only fasting remains obligatory even after manumission.
Supporting text
A dissenting opinion, held by Ibn Sirin, 'Ata', Al-Nakha'i, Al-Hakam, Hammad, Al-Thawri, Abu Ubayd, and the Companions of Ra'y, mandates that manumission becomes obligatory if the person gains the means before fulfilling the obligation with the substitute act (fasting), drawing an analogy to one performing Tayammum (dry ablution) who subsequently finds water before praying.