Vidhi nishedha is a prohibitory injunction of vidhi (sacred precept) in Hinduism. Purva Mimamsa lays down the rules of interpretation of Vedic sentences and is therefore known as vakya-sastra (the science of sentences). It divides Vedic sentences into vidhi, niyama, parisamkhya, nishedha and arthavada. Vidhi nishedha refers to one kind of Vedic sentence.
Vidhi is a sacred precept which enjoins something for the first time (vidhiratyantam aparaptau). The usual illustration is ‘a person desirous of heaven should perform yajna with soma.’ (svargakamah somena yajeta). That a pleasant place like heaven exists and that it can be obtained by soma yajna is known for the first time. Therefore, this is a vidhi.
Mimamsakas classify the vidhi sentences into four groups
Utpattividhi (vidhi of origin) – example he performs agnihotra. This is the original vidhi.
Viniyogavidhi (vidhi of application). (Example – He performs yajnas with curd). Application of curd is laid down; therefore this is vidhi of application.
Adhikaravidhi (vidhi of authority). It tells about on who is authorized to own the fruit of the yajna (Example – One desirous of heave should perform yajna). Thus, the fruit goes to one who is desirous of heaven. Therefore this is adhikara vidhi.
Prayoga Vidhi (vidhi of performance). It tells about the order of performance. (Example: Having taken a handful of grass, one constructs the altar.) Here the order is laid down; therefore it is the vidhi of performance.
Nishedha is prohibition. If a certain action during the performance of a ritual is harmful to the sacrifice or to the ritual itself, a prohibitory injunction is laid down. As a vidhi enjoins a person to do something, so also a nishedha deters him from doing something which is harmful. (Example: One should not see the rising sun). This is a prohibitory injunction, as it is against the vow one has taken.