KAṬHA UPANISHAD · 1.2.19

हन्ता चेन्मन्यते हन्तुँ हतश्चेन्मन्यते हतम् ।
उभौ तौ न विजानीतो नायँ हन्ति न हन्यते ॥ १९॥

hantā cenmanyate hantum̐ hataścenmanyate hatam ।
ubhau tau na vijānīto nāyam̐ hanti na hanyate ॥ 19॥

If the slayer think that he slays, if the slain think that he is slain, both of these have not the knowledge. This slays not, neither is He slain.