Ḥiyal (حيل, singular ḥīla حيلة "contortion, contrivance; device, subterfuge") is a term for "legalistic trickery" in Islamic jurisprudence. The main purpose of ḥiyal is to avoid straightforward observance of Islamic law in difficult situations while still obeying the letter of the law. An example of hiyal is the practice of "dual purchase" (baiʿatān fī baiʿa) to avoid the prohibition of usury by making two contracts of purchase and re-purchase (at a higher price), similar to the modern futures contract. Views on its admissibility in Islam have varied by schools of Islamic jurisprudence ( Madhhab), by time period, and by type of ḥiyal. A substantial literature on such tricks has developed in the Hanafi school of jurisprudence in particular.