Must the entire debt be paid before any portion of the mortgaged property can be released?

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There is a consensus among scholars known to Ibn al-Mundhir that a person who pledges property for a debt cannot reclaim a portion of the pledge after paying only a part of the debt; nothing can be released until the creditor's right is fully satisfied or the creditor explicitly absolves the claim concerning that portion. This view is held by Malik, Thawri, Shafi'i, Ishaq, Abu Thawr, and the companions of Ra'y. The evidence is that the pledge is a security for a right, and thus it cannot cease to exist except by the cessation of the entire right, analogous to a guarantee or testimony.