“He is to be sold and another slave substituted in his place.” Judge Abū Ya‘lā cited this report in al-Ta‘līq, in the discussion of emancipating a slave pledged as security.

Abū al-Barakāt said:

“He thus treated the slave’s refusal as equivalent to his becoming unserviceable.” That is, he must be compelled to perform all the work, just as a hirer is compelled, even though his refusal is unlawful. The impossibility of benefiting from him in this manner was treated as equivalent to his becoming unserviceable, in consideration of the interests of the endowment.

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As for replacing a mosque with another to serve a beneficial purpose, even though the original mosque remains usable, there are two views within Ahmad’s school. His followers differed on this matter, but permissibility is more clearly supported by his explicit statements and evidence. No explicit statement from him supports the other view; rather, his followers relied on the implications of his written words. He often rules that this is permissible when there is a need. This may mean that permission is restricted to cases of need; alternatively, he may have singled out such cases because that was what he had been asked about and needed to explain.

Abū Bakr ‘Abd al-‘Azīz discussed this at length in al-Shāfī, from which Zād al-Musāfir was abridged. He said: Al-Khallāl narrated to us: Sālih ibn Ahmad narrated to us: My father narrated to us: Yazīd ibn Hārūn narrated to us: Al-Mas‘ūdī narrated to us, from al-Qāsim, who said:

“When ‘Abd Allāh ibn Mas‘ūd—may Allah be pleased with him—arrived at the public treasury, Sa‘d ibn Mālik had already built