Is it permissible to use half the value of sold land to pay off a debt and obligation, and distribute the other half as Sadaqah in fulfillment of a vow, with the possibility of distributing the Sadaqah in stages?

A vow (nadhr (definition)) is not عقد (contractually binding) unless it is expressed in a صيغة (formulation) that indicates commitment. A mere statement of "I will do" is not considered a vow. If the vow is binding, then it is obligatory to give out the value of the land in charity. It is preferable to hasten in doing so, to avoid the differing opinion of those who deem immediate fulfillment obligatory. However, if the fulfillment of the vow is delayed, then there is no blame upon the one who made the vow according to many scholars who hold that its fulfillment can be done at leisure. In this case, it is permissible to spend from the value of the land while the expended amount remains a debt, as a vow to be fulfilled when possible. Nevertheless, it is more prudent to hasten in fulfilling it to absolve oneself of responsibility.