Śatapatha Brāhmaṇa ("of a hundred paths") 5.3.5.29

5.3.5.29

athāsmai tisra iṣūḥ prayacati | sa yayā prathamayā samarpaṇena parābhinatti saikā seyam pṛthivī saiṣā dṛbā nāmātha yayā viddhaḥ śayitvā jīvati vā mriyate vā sā dvitīyā tadidamantarikṣaṃ saiṣā rujā nāmātha yayāpaiva rādhnoti sā tṛtīyā sāsau dyauḥ saiṣā kṣumā nāmaitā hi vai tisra iṣavastasmādasmai tisra iṣūḥ prayacati

He then hands him three arrows. That first-one by which he pierces on shooting, that is one, that one is this earth, that one is called 'dribâ.' And the one by which (the enemy) being pierced lies either living or dead, that is the second, that is this air, that is called 'rugâ.' And the one with which he misses (his aim), that is the third, that is yonder sky, that is called 'kshumâ.' For these are the three (kinds of) arrows: therefore he hands him three arrows.