What is the expiation for a person prevented from Hajj who cannot offer the sacrificial animal (hady)?

Primary text

If the prevented person is unable to offer the hady, the requirement transitions to fasting ten days, after which he may dissolve the Ihram. This view is held by Al-Shafi'i, according to one of his two opinions. The evidence supporting the necessity of an alternative lies in the fact that it is a blood sacrifice (damm) necessitated by Ihram, and thus must have an alternative, similar to the hady for Tamattu' or for violations involving perfume or wearing clothes. The omission of explicit mention in the text does not preclude deriving an analogy from similar obligations. The transition to fasting ten days is mandatory, analogous to the replacement for the Tamattu' hady, and he cannot dissolve Ihram until after fasting, just as one who finds the hady cannot dissolve Ihram until after slaughtering it.