Is it permissible to annul a contract with a first contractor after signing it, and contract with another contractor for a lower price?

Subcontracting is permissible, provided that the property owner does not stipulate that the original contractor must perform the work himself, and that the original contractor's personal identity is not a matter of consideration for the property owner. The contracting agreement is a binding contract that cannot be rescinded except with the consent of both parties. If the original contractor agrees to rescind the contract, there is no objection; otherwise, the contract must be adhered to. The contracting agreement is permissible whether the contractor provides both the labor and the materials (manufacturing contract - istisna') or provides only the labor (service contract - ijarah (definition) 'ala al-'amal), and it is binding on both parties if its pillars and conditions are met.