A solidarity guarantee is a type of guarantee in which the guarantor loses the reserve status of the debtor's commitment while their obligations remain subsidiary to the debtor, and as a result, it is not permissible for the guarantors to pay in installments, stripping, or claim them before claiming the debtor; it is, therefore, harsher than a simple guarantee. The solidarity guarantee is historically earlier than the simple guarantee because Roman law defined it in its early ages. It is also widely known in Islamic jurisprudence. Although the general rule is that solidarity is not supposed to be in guarantees, the UAE and Jordanian laws have not adhered to this rule since they have agreed that guarantees are solidarity once the guarantor undertakes to guarantee it without a need for an agreement on solidarity. Regarding the sources of solidarity in guarantees, they are multiple. For instance, a guarantor's solidarity may arise under an agreement; such solidarity may be provided for by law as in legal or judicial guarantees. In addition, commercial law states that solidarity in commercial guarantees does not only with debtors but also with other guarantors.