SB 6.9.11

After Viśvarūpa was killed, his father, Tvaṣṭā, performed sacrifice to kill Indra, saying, "O enemy of Indra, flourish to kill your enemy without delay." Indra became free of the sin after one year, at the beginning of Aśvina month. Leaving the forest where he performed austerities, he began to observe the ceremonies of that month. Tvaṣṭā, hearing of the death of his son, out of anger and grief produced a means of killing Indra. His intention was to kill the enemy Indra. Thus he prayed for increase of strength of the enemy of Indra. However, the same words can be taken to mean “increase the strength of Indra, the enemy.” Thus the meaning is the opposite. The word Indra comes from the root id which means great power. According to its group, it should have a high intonation. However, according to the rule samāsasya ca, [Note: Pāṇini 6.1.223] when the word occurs in a compound, the accent should come on the last word. As a tat-puruṣa compound Indra-śatruḥ the word Indra should have a low intonation. It then means “enemy of Indra.” If the word Indra has an accent in this compound it is bahuvrīhi compound, and means “Indra, the enemy.” This is according to bahuvrīhau prakṛtyā pūrvapadam: the first member of a compound preserves is original accent in a bahuvrīhi compound. [Note: Pāṇini 6.2.1] Tvāṣṭā pronounced the phrase with the accent on the word Indra, and thus the meaning of the sentence became “May the strength of Indra, the enemy, increase!” Indra became the killer of his enemies. The śruti says svāhendra-śatraḥ vivardhasva with this meaning. It is said in the teachings: mantro hīnaḥ svarato varṇato vā mithyā-prayukto na tam artham āha yathendraśakraḥ svarato ’parādhāt sa vāgvajro yajamānaṁ hinasti A mantra devoid of proper intonation and pronunciation with improper use does not fulfill its purpose. Thus by saying “enemy of Indra” improperly, the thunderbolt of the words kills the priest because of his offense.