Brāhmahatya (also known as Brahma Hatya) is Sanskrit for "the act of killing a Brahmin". Puranic Hinduism considers this act to be a major sin, worse than the murder of others.
Legend
In a story involving Indra and Vritra, Brāhmahatya is portrayed as a hideous crime. The killer and his/her descendents thereafter bear a curse. It is not limited to the killing of a Brahmin. It extends to the killing of all those creatures that are equivalent to a Brahmin.
Japa, tapa, homa, yagya, tarpan and shradh kriya can defeat the curse. Brahma dosha nivarana pooja is also mandatory. In such cases trimbaka pooja at triyambakeshwara and pinda daan at gaya is suggested. Ancient scripts state that the curse can be defeated by the darshana of round ek mukhi rudraksha, but it is very difficult to get the original one.
In Tiruvidaimaruthur Shiva temple, near Kumbakonam, an idol for Brahmahatya is present. The complete legend of this temple is associated with this curse.