What is the ruling if the contracted person is capable of performance but refuses, claiming incapacity?

Primary text

If the contracted person is capable of performing the payment and possesses what they ought to pay, yet refuses and claims incapacity, the master (*Sayyid*) has the right to rescind the *Kitabah*. This view is held by Al-Sharif Abu Ja'far and a group of later scholars of our school, aligning with the apparent meaning of Al-Khiraqi's statement that the master's right to rescind is conditioned upon the non-performance. This is the madhab of Al-Shafi'i.